Francis E. Lloyd — 20 — Carnivorous Plants 



Along the upper (ventral) surface of the cylindrical petiolar portion arises 

 very gradually a single ridge, the ala ventralis, which attains consider- 

 able depth further up the leaf (/ — 4; 2 — 12). At the same time 

 the leaf becomes expanded into a curved conical hollow vessel, ex- 

 tending to the mouth. As this point is approached the ventral wing 

 begins to show evidence of a double character in that its edge is longi- 

 tudinally fissured to form two parallel ridges which are continuous 

 with the edges (nectar roll) of the bell, which in this species has a very 

 peculiar form. The abaxial two-thirds are expanded into a cordate 

 "flap," the sides of which where they meet the adaxial part of the 

 bell become helicoidal. The edge of the helix can be seen to continue 

 as the edge of a convolute margin of the pitcher — the adaxial part 

 just mentioned which I have called the nectar roll, and which is noth- 

 ing more or less than the adaxial part of the bell. Troll's (1932) 

 description says that the abaxial part of the pitcher is lengthened as 

 the lid. This is true enough as far as it goes, but this and all other 

 descriptions, as far as I am aware, neglect to point out the nature of 

 the curious rolled margin around the adaxial limb of the opening. 

 At the midpoint of this rolled margin there is on the surface no sign 

 of its nature. Examination by means of sections, however, shows that 

 the two ridges of the ventral wing spread to right and left to continue 

 as its involuted margins. One is reminded of the volutes of the 

 capital of an Ionic column. To sura up in a word, the flap and nectar 

 roll are to be taken together as the edge of the pitcher, wide and 

 leaf-life abaxially and tightly rolled outwardly adaxially. 



But this comes out quite clearly in the juvenile form of pitcher, 

 found on seedlings and delicate shoots. These are slender, the tubular 

 portion being narrow and only very gradually widening toward the 

 mouth (2 — 13). This is surmounted by an overhanging hood-like 

 expansion, the margins of which do not become rolled along the ab- 

 axial reach of the mouth, but run obliquely, meeting to form the 

 ventral wing. According to this description the ventral wing is a 

 single structure below and double above, so far as external evidence 



goes. 



Mrs. Arber (1941) has recently argued that the lid in Sarracenia 

 "is merely a localized development of the collar". This may be 

 questioned on the evidence above stated, that the collar (nectar roll) is 

 not present in juvenile leaves. 



The whole of the outer surface of the mature pitcher is supplied 

 with scattered nectar glands (2 — 15, 16). It is also somewhat rough 

 and hairy with scattered trichomes (j — 2) with peculiar thicken- 

 ings in the form of waves of surface expansion rather than continuous 

 ridges, such as occur on the trichomes of the interior. The external 

 glands may be regarded, as Macfarlane suggested, as alluring in 

 function, leading creeping prey to the mouth. 



The internal surface shows, as Hooker pointed out, distinct zo- 

 nation. He recognized four zones and described them as follows. 

 Zone I (2 — 12) embraces the cordate emarginate flap. The epider- 

 mis carries stomata, glands and strong downwardly directed hairs. 

 The lower limit of this zonation is clearly marked by an irregular line 

 where the character of the epidermis cells abruptly changes. In zone 



