96 SCIENCE PROGRESS. 



5. The Sporophyl/s, 1 the essential reproductive organs, 

 including : — 



(a) The stamens, forming the andrcecium ; (b) 

 the carpels, forming the gynseceum or pistil ; 

 in Flowering-plants. 



But this enumeration by no means exhausts the possibili- 

 ties of leaves, for these various categories may themselves 

 exhibit polymorphy to a remarkable degree. For instance, 

 some of the cataphyllary leaves of the onion, which is nothing 

 but a subterranean bud, become enlarged to serve as de- 

 positories of nutriment ; again, the leaves belonging to the 

 category of euphylls present, besides the endless varieties 

 of their typical form, a wide range of modification, assum- 

 ing forms so diverse as that of spines in the Barberry, of 

 tendrils in the Pea, of tentacular leaves in the Sun-dew, of 

 pitchers in Nepenthes and Sarraceuia. 



What now is the evidence to prove material meta- 

 morphosis in the case of leaves ? When we have to deal 

 with simple metamorphosis, with metamorphosis that is 

 taking place within the limits of any one category of leaves, 

 the evidence is as convincing as that which I have adduced 

 with regard to stems and roots. For instance, no one has 

 ever suggested that the spiny leaf of a Barberry, or the 

 pitchered leaf of A T epenthes, is anything but a modifica- 

 tion of an ordinary foliage-leaf ; or that the nectary of the 

 Monks-hood is anything but a modified petal ; or that the 

 petaloid investment of the inflorescence of the Trumpet- 

 Lily (Richardia) is anything but a bract. The most super- 

 ficial observation would suffice to disprove any contrary 

 assertion. But when we go on to consider the possibility 

 of a orenetic relation existing between leaves of different 

 categories, we have a more complex problem to solve. 

 However, some satisfactory evidence on this point is forth- 

 coming ; based to some extent on the actual observation of 

 development, but mainly on the occurrence of intermediate 

 forms. The consideration of the cataphylls affords a good 



1 We owe this term to Schleiden, Grundziige der fvissensckaft/icke?i 

 Botanik, English Edition, 1849, PP- I 94> 34^- 



