THEIR FORMS AND FUNCTIONS. 469 
Nymphea alba, Linn., agrees closely with WV. tuberosa. 
In Nuphar (N. advena, Ait.), on the contrary, there are no 
stipules, but the petiole is dilated,into a membranous wing, which 
tapers upwards and thins gradually towards the margin. This 
sheath becomes gradually shorter in the younger leaves, till it forms 
a mere basal auricle. It assists efficiently in protecting the young 
leaves. 
The stem-bud of Victoria regia, Hook., is covered with slime 
secreted partly by the stipules, partly by peculiar hairs on the 
leaf-surface (Goebel, Pflanzen-biol. Schilderungen, vi. Wasser- 
pflanzen, vol. ii. p. 233). 
CRUCIFER. 
Cardamine Impatiens, Linn.—The petiole is grooved from the 
apex to the base, which is dilated, and serves to protect the younger 
leaves. Some of the lower leaves have rounded and thickened 
auricles, which in the upper leaves become prolonged into 
subulate, obtuse, faleate auricles clasping the stem. These are 
often called stipules. They really correspond to the auricles of 
other Crucifere, which are continuous with the margin of the 
leaf. 
In Heliophila crithmifolia, Willd., the stipules are subulate, 
glandular, and inserted on the very base of the petiole. The buds 
are protected by the dilated petioles. 
In H. amplexicaulis, Linn. f., the stipules appear to be entirely 
absent. The bud is protected by each pair of leaves in succession. 
In Iberis saxatilis, Linn., the stipular processes are subulate, 
bristle-like, and inserted on the stem close to the edges of the 
leaf. The terminal buds are effectively protected by the crowded 
imbricate leaves. A similar arrangement occurs in many allied 
species. In I. Garrexiana, All., the stipules are also subulate, 
but apparently glandular. In J. amara, Linn., the petiole is 
winged for a great part of its length, but exstipulate. 
VIOLAREZ. 
Hymenanthera is generally said to be exstipulate ; but H. crassi- 
folia, Hook. f. (fig. 2),.has small, scarious, pale brown or grey, tri- 
angular stipules inserted on the slightly dilated base of the petiole 
close to, and even apparently on, the stem. They are ciliate at 
the margin, and are often torn. They are only 1 mm. long, and 
212 
