SECT. I 



MORPHOLOGY 



37 



Fig. ZS.—Hellcborus foetidus. Foliage leaf (0 

 and intermediate forms between this and 

 the bract (h). (Reduced.) 



epiphytic Ferns belonging to the genera Polypodiuvi and Platyceriuvi 

 alternately bear stalked, pinnate leaves serving for assimilation, and 

 l)road, sessile, usually cordate NEST-leaves which serve to collect humus; 

 when, as mantle-leaves, they are 

 closely appressed to the substratum 

 they form humus by their rapid decay. 

 The humus thus collected or produced 

 is penetrated by the roots of the Fern Q^). 

 Scale Leaves possess a simpler 

 form than foliage leaves, and are at- 

 tached directly to the stem, without 

 a leaf-stalk. The}' exercise no assimi- 

 latory functions, and are more especi- 

 ally of service as organs of protection. 

 Scale leaves exercise their most im- 

 portant function as bud-scales (Fig. 

 36); they are then hard and thick, 

 and usually of a brown colour. They 

 most frequently take their origin from 

 the enlarged leaf-base ; in that case 

 the upper leaf either does not develop, 

 or exists only in a reduced condition 

 at the apex of the scale. The true 

 morphological value of scale leaves of this nature is very evident 

 in the bud-scales of the winter buds of the Horse-chestnut (Aesculus 



Hippocastanum) ; for, while 

 the outer scales show no per- 

 ceptible indications of an 

 upper leaf, small leaf-blades 

 can be distinctly recognised 

 at the apices of the inner 

 scales. In other cases the 

 scale leaves are modified stip- 

 ules (Fig. 36), and are then 

 also derived from the leaf- 

 base ; while, in other in- 

 stances, they correspond to 

 the enlarged, but still un- 

 differentiated, primordial 



Fio. .39.— Flower of Paeonia peregrina. k, Sepals ; c, leaVCS. The bud-SCalcs of 



petals ; a, .stamens ; r/, carpels. Some of the sepals, the Oak are the stipules of 



petals, and stamens have been removed to show the ■■ +1 1 ' f 1 i 1 



pistil, consisting of two separate carpels. (Half isaves tUC laminae 01 wniCil 



nat. size.) are Only represented by mliiute 



scales. Scale leaves, usually 

 colourless and in various stages of reduction, are found on rhizomes 

 (Figs. 23, 34), bulbs (Fig. 25), and tubers (Fig. 26). On the aerial 



