FOLIAGE AND SCALE LEAVES. 63 
nettle. Emergences are also found in many cases, especially where 
the veins project on the lower side. (For SHEATH, cf: p. 154.) 
We next come to the consideration of SrrpuLes (cf p. 53). 
These are not always of the same nature. In the pansy, for 
example, they are extremely large and /oliaceous or leaf-like, 
and very likely correspond to the lateral lobes of a ternately- 
parted sessile leaf. The same, or something similar, appears to 
be true of many other such stipules, as perhaps in the case of 
the bean, pea, &c., where they look like a basal pair of leaflets. 
In fact, they may be the sole organs for performance of the leaf 
functions, as far as nutrition is concerned. The wild-peas, be- 
longing to the genus Lathyrus, illustrate in a very interesting 
way the mutations to which the regions of the leaf are liable. 
There are several British species. In one of these, the black 
pea (Lathyrus niger), the midrib of the pinnate leaf ends in a 
point ; there are fair-sized stipules, and several pairs of leaflets. 
Another species, the blue marsh-pea (LZ. palustris), has leaves 
tendrilled at the ends, larger stipules, and fewer leaflets. The 
leaves of the meadow-pea (L. pratensis) possess only one pair of 
leaflets and more tendrils. Lastly, in the yellow pea (L. Aphaca), 
the whole leaf is converted into a tendril, with the exception of 
the stipules, which are extremely large. Curiously enough, there 
is one species of Lathyrus, the grass-pea (L. Nissolia), in which 
neither leaflets nor tendrils are present, and the stipules are very 
small. The leaf-axes are here converted into phyllodes shaped 
like grass leaves. This condition is led up to by one or two other 
species where the petiole is winged. 
Many stipules are membranous, and very unlike the foliaceous 
examples already mentioned; and also they are not necessarily 
in the form of two free expansions, but may be united in various 
ways. Examine, for instance, a rose leaf, in illustration of the 
latter point. The petiole is sheathing at the base and bordered 
by a green wing on either side, which ends in a pointed lobe some 
distance from the first pair of leaflets. These two wing-like pieces 
are called adnate stipules, from the idea that they represent two 
of these structures adherent to the petiole. Such stipules are 
probably simply surviving bits of a once more extended wing. 
In many roses the adnate stipules are much smaller and not 
green. ‘This is also the case in clover. . A pair of stipules may 
unite in the leaf-axil to form an azillary stipule. Something 
akin to this is found in a membranous /zgule, which in grasses 
projects from the upper side at the junction of sheath and lamina 
(fig. 10). Indeed, this and many undoubted stipular structures 
appear to belong to the leaf-sheath. Two stipules may also be 
united into an opposite stipule, placed on the opposite side of the 
