the stool, and cuttings from these had been grafted by a Cretan farmer on the ordinary plane tree and were preserving the evergreen habit.(A.H.)
The stellate tomentum, which covers the young leaves of the plane, is gradually cast off; and floating in the air, has been found in some parts of Europe to produce serious bronchial irritation. This was known to the ancient Greeks,[1] being mentioned by Galen and Dioscorides. In Alsace-Lorraine, the planting of plane trees is forbidden in the vicinity of schools; and workmen in nurseries on the Continent, where young trees are raised, are often affected.[2] We have, however, not heard of any complaint of this happening in England.
The young leaves and shoots of var. acerifolia are frequently affected by a disease,[3] caused by the fungus known as Glœosporium nerviseguium, Saccardo, which in early summer attacks the nerves first and soon causes them to wither. Small black spots appear on the dead parts, which are the conidia of the fungus. In England, it is remarkable that the true oriental plane appears to be practically immune from the attacks of this fungus, though its leaves are sometimes blotched between the veins. Mr. Massee informs us that after a thorough examination of dried and living material, he has failed to find the slightest evidence in support of the statement that Glœosporium nerviseguium is parasitic on typical P. orientalis. The London plane is almost invariably affected, though less in London than in the country, where almost everywhere some of the leaves and young shoots become brown and wither; but the healthy growth of the tree is scarcely ever seriously interfered with. Some gardeners believe that this withering is due to cold winds and late frosts; but, though leaves may be injured by climatic conditions, this fungus is undoubtedly the principal cause. A plane tree, var. cuneata, in the Cambridge Botanic Garden, which had the habit of var. acerifolia, had the leaves badly attacked in June 1907. A tree, 30 feet high, of the same variety, at Grayswood, had the young wood seriously injured by a fungus, which Mr. Massee identifies with Glœosporium.
The fungus is apparently more severe in its attacks on the Continent; and at Ghent in 1891, all the plane trees lost their leaves.[4] In the United States, the occidental plane[5] is very liable to be attacked by this fungus, and as a street tree in New England is unsuccessful on that account, though P. acerifolia succeeds as well as it does in England.
Klebahn[6] states that Glœosporium nerviseguium occurs more especially on P. occidentalis, less frequently on P. orientalis. He believes that G. nerviseguium is only a conidial form of a higher fungus, called Guomonia Veneta, Klebahn.(H.J.E.)
- ↑ Cf. Gard. Chron. iii. 370 (1888).
- ↑ Carriére, Rev, Hort. 1890, pp. 370, 435.
- ↑ Cf. Massee, Plant Diseases, 284, f. 76 (1903).
- ↑ Cf. Gard. Chron. x. 491 (1891).
- ↑ Cf. Garden and Forest, 1891, p. 591, 1896, p. 51, and 1897, p. 257. In an article on Leaf-blight of the Plane Tree, by Murrill in Journ. N. York Bot. Garden, viii. 157 (1907), an account is given of an epidemic of the disease occurring this year in New York, believed to have been caused by the late and damp spring. Murrill observed the oriental plane to be attacked in Italy in 1906; and states that P. racemosa is also subject to the disease.
- ↑ Jahrb. Wissensch. Bot. xii. 515 (1905).
