Chapter III — 47 — Darlingtonia 



mouth are somewhat raised to form a low ridge. The twisting, charac- 

 teristic of the Darlingtonia leaf, has already begun. 



Case 3. A leaf 1.5 mm. long {6 — 3). The leaf base has elongated, 

 carrying the margins of its wings up some distance. Above, the rim 

 of the mouth has been extended down as a low double ridge and the 

 lateral reaches of the rim now begin to form the two sides of the ter- 

 minal fishtail of the mature leaf {6 — 6). The ascidium reaches well 

 down into the leaf base. 



Case 4. Leaf 2.6 mm. long {6 — 7). The wings of the leaf base 

 have now developed so that the distinction between this and the leaf- 

 blade is sharp. The double ridge, continuous with the two sides of 

 the mouth is longer and is raised up on the edge of the ala ventralis. 

 The close apposition of this with the apex of the leaf-base wings shown 

 by Troll for Sarracenia does not occur here. It has now become 

 clear that the double character of the edge of the ala ventralis is de- 

 rived from the rim of the mouth. If not so extended in Sarracenia, 

 yet the origin of the double edge is the same. In this case the twist 

 of the leaf is to the right. 



Case 5. A trifle older than case 2, not so old as case 3, in sagittal 

 section {6 — 4). Here can be clearly seen the identity of the side lip 

 of the mouth and the edge of the keel. The pore of the mouth is still 

 small. The section being truly sagittal, the other keel edge is not seen. 

 No indication of the nectar roll is yet visible. Advance beyond this 

 stage consists of the enlargement of the lateral reaches of the lips of 

 the mouth concomitant with the laying down of the nectar roll and 

 its continuation along the outer margins of the fishtail. 



Cases d, 7 and 8 {6 — 5, 6, 10). Successive stages following on 

 case 5, showing the development of the fishtail from the sides of the 

 mouth, the apex being now arrested and of slower growth. In cases 

 7 and 8, the outer marginal roll of the one side of the fishtail is seen, 

 and that it is continuous with the nectar roll which has also appeared. 

 The fold between the distal ends of the nectar roll has begun develop- 

 ment. 



Case g {6 — 16). Surface view of a somewhat later stage, about 

 like that shown by Goebel. The difficulty of interpretation is obvious. 



Case 10 {6 — 8). The dome has begun development and the tube 

 is twisted through 90 degrees. The distinction between the edges of 

 the wings of the leaf base has become obscure, except in transverse 

 sections (5 — 5). Seen in sagittal section the dome is represented in 

 6 — 9. The fold {6 — 10) has now come into a vertical position as the 

 dome has enlarged fore and aft, and the outer marginal roll of the one 

 side of the fishtail is seen continuous with the nectar roll, which has 

 pushed forward. The ventral surface of the fishtail is continuous with 

 the inside surface of the dome. 



In a word, all parts are now clearly defined, and the glands have 

 appeared. The final condition may be seen in various figures illustrat- 

 ing the mature leaf. At the time growth is complete, the leaf has 

 twisted through an angle of 180 degrees, though it may be as small as 

 90 degrees or as large as 270 degrees. The torsion does not involve the 

 dome. It is either to the right or left in any given plant (antidromy 

 of McClosky). 



