At their base they are provided with stipules, which are also modified to form the scales investing the winter buds.
- Leaf of Viola tricolor (Pansy) showing the large leafy stipules (s).
The opposite or alternate leaves have a pair of small stipules at the base of the stalk and a palminerved blade.
At the base of the leaf the spiny stipules are seen.
The stipules are generally two in number, and they are important as supplying characters in certain natural orders.
Stipules may be large or small, entire or divided, deciduous or persistent.
24) the true leaves are stalked and crenate, while the stipules s are large, sessile and pin natifid.
In Lathyrus Aphaca and some other plants the true pinnate leaves are abortive, the petiole forms a tendril, and the stipules alone are developed, perform ing the office of leaves.
- Pitcher sionally happens Orange (CitrusAuran- (ascidium) of a species that the stipules on tium), showing a of Side-saddle plant the two sides unite winged leafy petiole p, (Sarracenia purpurea).
In the case of alternate leaves, the stipules at the base of each leaf are sometimes united to the petiole and to each other, so as to form an adnate, adherent or petiolary stipule, as in the rose, or an axillary stipule, as in Houttuynia cordata.
In the development of the leaf the stipules frequently play a most important part.
The stipules are sometimes so minute as to be scarcely distinguishable without the aid of a lens, and so fugacious as to be visible only in the very young state of the leaf.
At the base of the leaflets of a compound leaf, small stipules (stipels) are occasionally produced.
The leaves of barberry and of some species of Astragalus, and the stipules of the false acacia (Robinia) are spiny.
In Leguminous plants (the pea tribe) the pinnae are frequently modified to form tendrils, as in Lathyrus Aphaca, in which the stipules perform the function of true leaves.
In many plants, as already noticed, phyllodia or stipules perform the function of leaves.
The divergence is expressed left to right, the other is right to left, in the altered laminae or of the enlarged petiolary sheath, or of stipules, as in the fig and magnolia, or of one or two of these parts combined.
Spadicigera, the large thorn-like stipules are hollow and afford shelter for ants, which feed on a secretion of honey on the leaf-stalk and curious food-bodies at the tips of the leaflets; in return they protect the plant against leaf-cutting insects.
The spring when the delicately transparent green leaves are bursting from the protection of the pink and white stipules, which have formed the bud-scales, and retains its fresh green during early summer.
The leaf is usually provided at the base of the leaf-stalk with stipules, which are inconspicuous, or large and leafy; and the stalk is also furnished with one or more glandular excrescences, as in some cases are the leaf itself and the bracts.
In Ceratozamia the broad petiole-base is characterized by the presence of two lateral spinous processes, suggesting stipular appendages, comparable, on a reduced scale, with the large stipules of the Marattiaceae among Ferns.
Many case's of what was considered chorisis are in reality due to the development of stipules from the staminal leaf.
Thus in Dicentra and Corydalis there are six stamens in two bundles; the central one of each bundle alone is perfect, the lateral ones have each only half an anther, and are really stipules formed from the staminal leaf.
In Potentilla and allied genera an epicalyx is formed by the development of stipules from the sepals, which form an apparent outer calyx, the parts of which alternate with the true sepals.
The magnificent Devonian Fern Archaeopteris hibernica, with a somewhat Adiantiform habit, bore special fertile pinnae; the fructification is still imperfectly understood, but the presence of stipules, observed by Kidston, has been adduced in support of Marattiaceous affinities.
The stipules of the leaves act as protecting scale-leaves in the winter-bud and fall when the bud opens in spring.