a considerable number of Dicotyledonous and Monocotyledonous plants, and many ferns.

A common example occurs in any abandoned field or waste ground bordered by Elm trees. The young plants which shoot up everywhere are not seedlings, but are formed by adventitious buds on the roots of the old trees; the considerable distance at which they appear from the parent emphasises the great length of the roots. Similarly, when a tree is cut down the ground becomes covered with a thick growth of young shoots, springing up rapidly, at the expense of the nourishment stored up in the roots which remain in the ground. Such shoots are also common in Poplars, Limes, many fruit trees, &c.

Accidental adventive buds are those which appear if the plant is maimed or wounded; or if a leaf, say of Begonia, is detached from the parent plant and placed on damp earth.

Goebel, in his recently published 'Organographie,' figures an interesting case of the growth of a new plant at the end of the stalk of a detached leaf. The plant in question is a garden hybrid belonging to the same family as Gloxinia (fig. 21). The leaf was taken from a plant which was just about to flower, and the adventitious shoot has straightway produced flowers.

To eradicate Docks from a garden the whole plant must be removed, as adventitious buds will arise on any broken piece of root which is left behind The same

applies to Dandelions or Plantains. The natural adventive buds appear on definite parts of the plant, according to the species; in accidental adventive buds the place of origin depends on that of the injury.

FIG. 21.-ACHIMENES HAAGEANA, showing development of a new flowering plant consisting of root and flowering-shoot.

Adventitive shoots may arise, like normal shoots, exogenously; but endogenous development generally occurs when they arise from older parts of stems or roots. In some cases they are formed by the direct conversion of the growing-point of a root, as in Bird's Nest Orchid (Neottia Nidus-Avis), Catasetum tridentatum, &c.

CHAPTER II

ON STIPULES

VAUCHER, in his 'Histoire Physiologique des Plantes,' writing on the Rock Roses (Helianthemum), observes:

FIG. 22.--SHOOT OF HELIANTHEMUM VULGARE. Slightly enlarged. 'J'indique dans ce genre deux principaux objets de recherche. Le premier est la raison pour laquelle certaines espèces ont des stipules tandis que d'autres

en sont privées.' This suggestion started me on the present inquiry. No one, so far as I know, had attempted to answer Vaucher's question, which is one of considerable interest, and might be asked with reference to several other groups besides the genus Helianthemum. The results of my observations have been embodied in several Memoirs which the Linnean Society has done me the honour to publish in their Journal,' and I now propose to bring together those portions which seem to be of general interest.

FIG. 23.-SHOOT OF HELIANTHEMUM CELANDICUM. Slightly enlarged.

Fig. 22 represents a shoot of Helianthemum vulgare (the Common Rock Rose), with stipules; Fig. 23, one of Helianthemum celandicum, which has none.

Malpighi, in his' Anatomy of Plants' (1671), seems to have been the first who mentions these organs, which he terms (p. 29) 'folia caduca,' in opposition to the ordinary and generally, though by no means always, more permanent leaf-blades. Almost at the same time (1672) they were noticed and described by our countryman Grew, who called them interfoils. Linnæus gave them

1 The Anatomy of Plants, p. 146.

the name of stipules; from stipula, a little straw. This term happily expresses their appearance in such a case as that of the Beech, but they present great differences in size, form, and texture.

The Peach (fig. 24) and Portugal Laurel (fig. 25) are good examples of a typical simple leaf with a pair of stipules at the base of the stalk.