above the cotyledons the first pair of true leaves are produced, which are opposite, compound, digitately five-foliolate, and closely resemble the adult foliage except that they are smaller in size. Successive pairs of similar leaves follow on the stem, each pair being placed decussately with reference to the pair immediately below it.
Abnormal Flowering
The horse-chestnut sometimes produces a second crop of flowers in autumn, which appear in much smaller panicles than those of spring. This is due to the premature fall of the leaves in July or August, usually following an excessively dry season. The buds are stimulated to premature energy and put forth young leaf-shoots, which are terminated by flowers. This phenomenon, which is equivalent to an anticipation of the opening of the buds by several months, as they would normally open in the following spring, is frequently observed in the trees planted in the boulevards of Paris.[1] In the dry season of 1884, a single tree at Kew produced small panicles of flowers in September, after previously shedding nearly all its leaves. In the following year it produced a few panicles of the ordinary size. At Hythe,[2] near Southampton, a horse-chestnut is reported to have bloomed and fruited three times in 1868, once in spring, again after the rain which succeeded the long drought, and a third time in September.
Identification
In summer the common horse-chestnut is unmistakable. The only other species with large sessile leaflets, Æsculus turbinata, is easily distinguished by their regular crenate serration. In winter the twigs and buds show the following characters:—Twigs stout, brown, glabrous or minutely pubescent towards the tip; lenticels numerous. The large opposite leaf scars, flat on the twigs with no prominent cushion, are joined by a linear ridge, and vary in shape, the larger being obovate with seven bundle-dots, the smaller semicircular or crescentic with usually only five dots. Buds very viscid, larger than in the other cultivated species; the terminal much exceeding the lateral buds in size, occasionally absent, and replaced by the saddle-shaped scar of the previous year's inflorescence; scales imbricate, the external ones in four vertical ranks, rounded at the apex, glabrous, not ciliate, dark red-brown. The buds contain the next year's shoot in an advanced state of development, flowers being visible in them in October. The scales are morphologically equivalent to leaf-bases. In the interior of the bud, scales are observable with traces of leaf-blades, which gradually pass into the true leaves, visible in the upper part of the bud.
Varieties
1. Var. flore pleno, Lemaire, Illust. Horticole, 1855, ii. t. 50. A variety with double flowers, the pistil even in some cases becoming petaloid. Mr. A.M.
