The Trees of Great Britain & Ireland/Volume 2/Thujopsis
THUJOPSIS
- Thujopsis, Siebold et Zuccarini, Fl. Jap. ii. 32 (1842).
- Thuya, Bentham et Hooker, Gen. Pl. iii. 427 (1880).
- Cupressus, Masters, Journ. Linn. Soc. (Bot.), xxx. 19 (1893) and xxxi. 363 (1896).
This genus is considered by many authorities to be merely a section of Cupressus or of Thuya. The foliage and cones, however, are remarkably distinct, and justify its retention as a separate genus.
Evergreen trees, belonging to the tribe Cupressineæ of the order Coniferæ, with reddish bark scaling off in longitudinal shreds. Branches in false whorls or scattered, giving off secondary branches, which terminate in very flattened branch-systems, disposed in horizontal planes. These resemble in their general arrangement those of Thuya and Chamæcyparis, and are mostly tripinnate, all the axes being covered with small coriaceous leaves, adnate in part of their length, and arranged in four ranks in decussate pairs. The leaves on the main and ultimate axes differ only in size.
The ventral and dorsal leaves are flattened and ovate or spathulate, with rounded apices; the lateral leaves are carinate, more or less spreading, with a slightly acute apex, which is bent inwards. The dorsal flat leaves are shining green, and marked with a central ridge, which is often hollowed in the middle line. The ventral flat leaves have a central green ridge, with a concavity white with stomata on each side. The lateral leaves, green on the dorsal side, exhibit a single stomatic concavity on their ventral side.
Flowers monœcious, solitary, and terminal, the male and female flowers borne on separate lateral branchlets as in Thuya. Male flowers cylindric, ¼ inch long, with six decussate pairs of stamens. Female flowers with five ovules on each scale. Cones globular, almost erect, with eight clavate, woody scales, in decussate pairs from a central axis, the upper pair abortive. Seeds three to five on a scale, laterally winged, the wing not notched at the summit.
The seedling[1] resembles that of Thuya plicata, but has broader and very blunt cotyledons, with shorter and broader primary leaves.
THUJOPSIS DOLABRATA
- Thujopsis dolabrata, Siebold et Zuccarini, Fl. Jap. ii. 34, tt. 119, 120 (1842); Franchet et Savatier, Enum. Pl. Jap. i. 469 (1875); Shirasawa, Icon. Essences Forest. Jap., text 27, t. xi. 18–34 (1900).
- Thuya dolabrata, Linnæus, Suppl. Pl. System, 420 (1781); Masters, Jour. Linn. Soc. (Bot.), xviii. 486 (1881), and Gard. Chron. xviii. 556, fig. 95 (1882); Kent, in Veitch's Man. Conif. 236 (1900).
The species has been described in detail above.
Two well-marked geographical forms occur, both confined to the main island of Japan:—
1. Var. australis (var. nova). A small tree 40 to 50 feet in height, or a shrub growing as underwood in the dense shade of forests. As a tree it has a slender trunk, with drooping branches and a narrow pyramidal top. Branchlets very flat and only slightly overlapping, the lateral leaves ending in acute points bent inwards. Cones broadly ovoid, with scales thickened at the apex, which is prolonged externally into a blunt triangular process. This is the form which is known in cultivation in Europe, and described and figured in the works cited above.
2. Var. Hondai, Makino.[2] A larger tree, attaining 100 feet in height, with a stem of over 3 feet in diameter. The branch-systems are more densely ramified, the branchlets being placed close together and overlapping one another by their edges more than is the case in the preceding variety. The leaves also are smaller, whiter underneath, and crowded more closely on the shoots; those of the lateral ranks being usually blunt and not curved inwards at the apex. The cones are globular, with scales not thickened at the apex, which is devoid of the process so conspicuous in the other form, or merely shows it as an obsolete transverse minute mucro. The seeds appear to be more broadly winged, the wings being more scarious in texture.
This form has not yet been introduced. Elwes has brought home excellent specimens of it in fruit from the Uchimappe Forest, near Aomori, in the extreme north of Hondo. These differ in the characters given above from specimens of the ordinary form obtained by him in the forest of Atera, Kisogawa, and Yumoto (4000 to 5000 feet altitude) in Central Hondo. The smaller leaves, set more closely on densely ramified branchlets in this variety, may be due to the influence of dense shade. The difference in the cone is paralleled by what occurs in the fruit of the different geographical forms of Cryptomera japonica. I am inclined to think that var. Hondai is not a distinct species; but as it is very different, from the point of view of cultivators, it may conveniently bear the name Thujopsis Hondai.
Several horticultural varieties have been introduced, viz.:—
3. Var. lætevirens, Masters, Jour. Linn. Soc. (Bot.), xviii. 486.
- Thujopsis lætevirens, Lindley, Gard. Chron. 1862, p. 428.
- Thujopsis dolabrata nana, Gordon, Pinetum, ed. 2, p. 399.
A dwarf shrub having no definite leader, with slender and much-ramified branchlets, and very small and bright green leaves. This variety often shows acicular leaves, spreading all round the shoot, and is apparently a fixed seedling form. It was introduced in 1861 from Japan by J. Gould Veitch.
4. Var. variegata. This only differs from the ordinary cultivated form in having the tips of many of the branchlets pale yellow or cream colour. It was introduced by Fortune in 1861.
Distribution
Thujopsis dolabrata was discovered by Kaempfer,[3] who mentions it in his Amœnitates Exoticæ, p. 884, as "a kind of Finoki." His specimen is still preserved in the Natural History Museum at South Kensington, and was figured by Lambert[4] in his account of the species. Thunberg long afterwards (about 1776) sent specimens to Linnæus, who first gave a scientific description of the tree. Thunberg[5] cites the locality as follows:—"Crescit in regionibus Oygawæ et Fakoniæ, inter Miaco et Iedo." (A.H.)
Thujopsis dolabrata in Japan is known under the name of Hiba, and is found in a wild state north of about lat. 35°, and in the southern part of this area is a mountain tree only, occurring in the forest of the Kisogawa district from about 3000 to 5000 feet. In the vicinity of Nikko it is common between about 4000 and 6000 feet according to Sargent, but I only saw it here near Lake Yumoto where it did not appear to attain such large dimensions as farther north. The variety found in the forests of Atera is distinct in its fruit from the northern form. The excellent figure on Plate xi. in Shirasawa's Essences Forestières appears to be taken from the southern variety.
The northern form has been described by Makino as var. Hondai, but the latter is not mentioned either by Goto or Shirasawa, nor is it recognised as specifically distinct in any of the Japanese collections which I saw. Though the tree usually occurs in mixture with Tsuga at Nikko, and with Sciadopitys at Atera, yet in the extreme north of Japan, on the hills north of Aomori, it is found in pure forest on hills of volcanic formation from near sea-level up to about 3000 feet. An excellent account of the forest of Uchimappe is given in Forestry and Forest-Products of Japan, where it is stated that the mountains are of Tertiary formation, and the under-lying rock composed of tufa, sandstone, and slate. Pieces of this rock which I brought home have been examined by Mr. Prior of the British Museum of Natural History, who considers that in all probability they represent a rather basic andesite or basalt, but owing to the weathered and decomposed state of the specimens, satisfactory sections could not be made. I visited this forest in the company of Mr. Shirasawa in June, and after passing through the flat rice-fields which extend from the sea to the foot of the hills, entered the forest, which consists mainly of Thujopsis naturally reproduced, though here and there, trees of Quercus glandulifera, Magnolia hypoleuca, and other species occur, whilst Cryptomeria and Cupressus obtusa are planted in the valleys, and Larix leptolepis on those parts of the hills where the natural forest has been destroyed by fire. From observations taken at the meteorological observatory of Aomori, it appears that the climate of this part of Japan is cold in winter and the snowfall heavy, the thermometer falling in February to —15° Centigrade, and rising in September to 32°5° Centigrade; the average temperature for the whole year being 9°, and the average moisture 78 per cent. The average height of the trees here is about 70 to 80 feet, attaining in deep shady valleys 100 feet or perhaps more, and about 2 feet in diameter when closely grown, at the age of 150 to 180 years when it is considered ripe for felling.
The stems are often much curved at the butt from the pressure of the snow on the young seedlings, which require eight to ten years to get above its surface in winter, and these butts are usually cut separately and used for special purposes. The tree does not seem to have the power of reproducing itself from the stool, but produces abundant seed, which in dense shade germinates freely, though the growth of the seedlings is very slow at first.
The undergrowth of the forest is very different from what I saw in other parts of Japan, bamboo-grass (Arundinaria Veitchii) being much less prevalent, but in the damp places tall herbaceous plants were numerous, with Aucuba, Skimmia, and Ilex, and other evergreen shrubs on the drier ground, and many pretty liliaceous plants and orchids in places.
Goto says of this tree,[6] that it formed under the old regime, together with Cupressus pisifera, C. obtusa, Thuya japonica, and Sciadopitys, the so-called "Goboku" or Five Trees, which enjoyed careful protection at the hands of the feudal authorities; he also says that it is rarely planted, being regenerated naturally by seed, and that it forms extensive forests in a mixture with other conifers such as Thuya japonica and Pinus parviflora, in the mountains on the northern frontier of the province of Rikuchu, in Goyosan, and in the mountains of the Tone districts, Kozuké. It has lately come to be in great demand for railway sleepers.
Plate 60 (in Vol. I.) represents a dense growth of trees of this species in the forest of Uchimappe very similar to what I saw in the Kisogawa district at about 3000 feet. I am indebted to the Japanese Forest Department for the negative from which it was made.
The wood of Thujopsis is highly valued in those parts of Japan where it grows, on account of its great durability. This is proved by specimens shown at the St. Louis Exhibition, one of which had been used as a gate-post for eighty-three years, another as a plank in a fishing-boat for eighty-four years, others as railway sleepers in use for fourteen years. The wood has an aromatic smell, takes a fine lustrous polish when planed, and is yellowish white in colour, showing a fine grain, which makes selected planks from the butt length very ornamental. Exceptional 
Plate 60.
THUJOPSIS DOLOBRATA IN JAPAN
The wood weighs about 30 lbs. per cubic foot, and is worth at Aomori from 40 to 50 yen per 100 cubic feet, or about 1s. per cubic foot. It is much valued not only for joinery and building purposes, but for foundations, ship and boat building, as it is stronger and more resinous than other woods of the same character.
The bark also, which is thin, tough, and durable, is much used for roofing and for partitions and walls of out-houses, fences, etc.
Cultivation
T. Lobb sent a plant from the Botanical Garden at Buitenzorg in Java, to Exeter in 1853, which died; and soon after, Capt. Fortescue, a cousin of Earl Fortescue, brought a plant from Japan which was planted at Castlehill in 1859. But this tree, as I learn from Mr. Pearson, the head gardener, has been dead for some time, though plants raised from its cuttings are still growing at Castlehill and elsewhere.
In 1861 Mr. J.G. Veitch and R. Fortune sent seeds from Japan to the Chelsea and Ascot Nurseries, from which plants were raised and generally distributed, so that the tree is now common in England.
From what I have said of its habitat in Japan it is clear that though this tree is hardy as regards frost in winter, it requires conditions which are rarely found in England to bring it to any size, and, as a matter of fact, it has not yet become a tree anywhere except in Devonshire and Cornwall, though perhaps if seeds from North Japan are obtained the results might be better.
Though no doubt it has ripened seeds elsewhere, I have never obtained any which germinated, except from a tree planted about 1881 by Queen Alexandra in the Earl of Northbrook's grounds at Stratton Park, Hants, which I gathered in October 1900. One of these grew, and is now a healthy plant about 9 inches high. It seems to suffer less from spring frost than many Japanese and Himalayan conifers.
The finest tree that I have seen in England is at Killerton, which in 1902 measured 35 feet 6 inches in height and 2 feet 4 inches in girth. It is growing on a slope facing south-west in a peculiar soil, which Sir C.T.D. Acland describes as "Trap, soft below the surface, but hard after exposure. This trap overlies red sandstone, but is rather darker and more porous." This soil evidently suits most conifers admirably, as I have seen no other collection which contains so many fine specimens as this.
At Boconnoc, at Carclew, and at other places in Cornwall there are trees approaching this in height, but we have not seen any specimen above 15 to 20 feet in other parts of England, though as a bushy shrub 12 feet high it exists in most modern gardens. In Scotland it seems hardy in the west and in Perthshire, whilst at Castlewellan in Ireland it has attained 30 feet in height. At Powerscourt and Kilmacurragh, Wicklow, there are trees with the lower branches layering and forming numerous independent stems. (H.J.E.)