THEIR FORM AND FUNCTION. 233 
stipules, the latter being adnate to the petiole for a greater or 
less part of their length. 
Several other genera of Rosacex (Crategus, Pyrus, &c.) present 
us with cases of polymorphic stipules. In the Quince (Pyrus 
Japonica), for instance, we have the following series :—1st. 
The scales of the winter-bud are very broad, short, deeply 
trifid or almost tripartite, deep brown or black; the lateral 
lobes are the largest and are the stipules. 2nd. Fascicles of 
leaves are produced along the sides of the previous year’s wood, 
and the stipules on the outer ones are reduced to small blunt 
teeth. 8rd. Those towards the centre of the fascicle bear sub- 
ulate or linear stipules, with a distinct midrib. 4th. On the 
base of the elongating shoots the stipules are lanceolate, shortly 
stalked, acute, and one-nerved. 5th. The stipules gradually 
widen on succeeding leaves, till they become broadly and ob- 
liquely reniform, dentate, with the midrib nearest the anterior 
side and running into an acute point, copiously reticulate, shortly 
petiolate, foliaceous, with large auricles passing round the axis 
until they meet on the opposite side. The scales of the winter- 
bud persist for some time at least after the expansion of the 
leaves and offer some protection. There would be no need, 
nor room, for large stipules in the fascicles of leaves, as the 
older protect the younger. 
Stipules often disappear, or nearly so, when the leaves become 
fascicled in dense rosettes. The large reniform stipules are folded 
round the sides of the convolute leaves which enclose all the 
younger members; one leaf encloses the whole of the upper 
portion of the bud, while the stipules protect the lower lateral 
portions where the leaves narrow into the petiole. The inter- 
nodes are rather elongated, and the large stipules would be of 
importance or of use indirectly by increasing the area of leaf- 
surface. The petioles, I may add, are subterete. 
In the genus Spirea we find remarkable differences, offering 
an interesting analogy with those which occur in Viburnum. The 
simple-leaved species of the genus (S. lævigata, 8. Douglasii, 
S. tomentosa, &c.) have no stipules. The winter-buds are pro- 
tected by brown, ciliate scales, which gradually pass into truc 
leaves. On the other hand, the compound-leaved species have 
well-developed stipules. In S. sorbifolia, &c., they are lanceolate 
or oblanceolate and protect the buds. The winter-buds are also 
LINN. JOURN.—BOTANY, VOL. XXVIII. T 
