196 



PRINCIPLES OF PLANT-TERATOLOGY. 



18. "Enations" and Asctdia of Foliage-leaves.* — 

 These constitute some of the most remarkable r and 

 morphologically interesting teratological phenomena in 

 the vegetable kingdom, as they are also amongst the 

 most difficult to interpret. They are usually regarded 

 as the result of hypertrophy in the development of 

 the organ concerned. 



a. Ascidia as Leaf-appendages. — Those, firstly, will 

 be described which are so commonly met with in the 

 cabbage and which assume such varied and interesting 

 forms. Several lar^e leaves were observed which had 

 developed laminar outgrowths of considerable size 

 along the midrib of the upper surface, and also quite 

 small ascidia or pitchers on long stalks in the same 

 position ; the surfaces of the enations which were 

 opposed to the (upper) surface of the leaf were 

 morphologically the lower. The enations often assume 

 most carious shapes : elongated structures with but 

 little laminar development very often, and when this 

 occurs, taking the form of semi-pitcher-shaped bodies 

 produced here and there on a vein-like stalk. The 

 enations usually arise from the midrib or from the 

 other larger veins. On one leaf was observed a long- 

 stalked small pitcher or ascidium springing about 

 two- thirds of the way up the midrib, this being 

 unusually thickened below the pitcher's insertion 

 (PI. XV, fig. 2) ; the outer surface of the pitcher was 

 morphologically the upper surface, and being opposed 

 to the upper surface of the leaf, it thus obeyed the law 

 of laminar inversion according to which opposed 

 laminar surfaces are similarly constituted (PI. XVII, 

 fig. 2, and fig. 53 in text). 



On other leaves stalked or sessile pitcher-like struc- 

 tures have been seen arising from the lower surface of 



* This phenomenon has been introduced under the section <f Simplifica- 

 tion" because of the tendency, in the majority of leaves producing- ascidia 

 and enations, towards the reduction in size, representing- as they do (see 

 infra) stages in the formation of anther-structure ; and an anther is an 

 exceedingly reduced leaf-blade. It is, at the same time, true that both 

 anthers and the foliage-leaves treated of under this heading are, in their 

 actual structure, more highly differentiated than normal foliage-leaves. 



