Francis E. Lloyd — 198 — Carnivorous Plants 



Each lobe, when the trap is mature and is in the set posture 

 (ready to catch prey), is concavo-convex from within out. But the 

 curvatures are not simple spherical ones. It will be seen by the fig- 

 ures herewith that two oval zonal regions, one on either side of the 

 midrib, are fiat (ig — 8, 21-23) and are subject only to slight cur- 

 vatures under stress during the closure of the trap. From this flat 

 middle region, the lobes spread with a maximum curvature along the 

 transverse middle line. Here the curvature is much like that of the 

 ribs of a vessel amidships. This is the principal region of motion 

 during closure (2, ig — 22-23). The next region is one of compara- 

 tively Httle inward curvature (5, 19 — 23) as far as the margin, which 

 is sharply bent back inwardly to form a valve edged with a row of 

 sharp teeth. The whole looks hke a widely opened clam or mussel 

 (ig — 21a). This is what one sees looking merely at the outer form. 

 When the thickness of the lobes is examined, the following is found. 

 The inner half, along the midrib, is thick and relatively rigid. This 

 half (the thick region) includes the place of greatest curvature, to- 

 gether with a measure beyond (again as seen in a transverse section 

 normal to the midrib at its middle point) (1-3, ig — 23). Anatom- 

 ically it consists of three courses of cells, the two slender celled epi- 

 derms which are thin, enclosing a single course of very large 

 thin-walled cells, the long axes of which run transversely the leaf 

 (ig — 10, 11). This structure is continued around the sharp bend 

 of the motile region, which is somewhat thinner than elsewhere, into 

 the sides of the trap somewhat less than half-way to the free mar- 

 gin. At this point the lobe suddenly thins, the middle course of large 

 cells ceasing. The lobe then consists of a very thin membrane con- 

 sisting of only the two epiderms juxtaposed, and so it continues 

 quite to the inturned margin which forms the valve. The valve 

 itself is thicker again, due to the enlargement of the epidermal cells, 

 giving it a useful firmness to make it eftective. Since only the mid- 

 dle transverse structure as seen in section has been examined, some 

 details concerning the curvature of the lobe margins must be men-' 

 tioned. 



The stiff region of the trap wall along the midrib does not extend 

 its full length, so that, beyond certain points, the proximal and distal 

 parts of the walls are thin and, when the trap is closed, readily ap- 

 proach each other so as to lie juxtaposed. As the marginal valve 

 does not reach the midrib — it becomes narrower as it approaches 

 it and quite ceases 0.75 mm. away — there are left two spaces, one 

 at the apex and one at the base of the blade, which, when the trap 

 is closed, can allow the escape of water, while elsewhere the valve 

 acts to prevent the escape of prey during the whole course of closure 

 of the trap. This escape of water is necessary to permit the two 

 thin regions of the lobes to approach and to become mutually ap- 

 pressed. This is possible because the thin region of the free-side 

 lobe inclines to bend when pressed against the bristle-side lobe, 

 due to its set acquired during development, so that when the 

 trap is fully closed, the thin regions of the two lobes dish into one 

 another as during development {ig — 21, 22), crowding the prey, if 

 caught, into the digestion cavity. Before the act of closure is looked 



