Francis E. Lloyd — 250 — Carnivorous Plants 



hinge, the cells are elongate, and have numerous very small but- 

 tresses, difficultly seen. That is to say, the cells in the regions of 

 maximum bending have zigzag walls with many buttresses. Where 

 the door is stiffest, i.e., in the middle piece, the buttresses are at a 

 maximum in numbers and size. In these cells also the walls are thick, 

 especially the outer. 



Looking at the inner face of the door, we note a different pattern. 

 With the central hinge as a center, the inner course consists of elon- 

 gated cells radiating from this center to this circumference {24 — 9). 

 The closer to the center the shorter the ceUs become, so that at the 

 center they are isodiametric and thickly studded with buttresses. 

 Below the center, the cells of the inner course of the middle piece 

 are also isodiametric and match the outer course of cells in the degree 

 of buttressing. From here, tending toward each side of the door, the 

 cells become longer and run along the selvage parallel to it. This 

 seems at first glance simple enough, and it seems surprising that the 

 cells of the whole inner course should have been more than once 

 described as isodiametric. The mistake is easily explained, for when 

 the inner surface of the door is examined without flattening it out, 

 to do which it must be fully plasmolysed, a series of concentric lines 

 can be seen {24 — 9; 2g — 3). Darwin saw them. They were cor- 

 rectly understood first by Meeerhofer. They are nothing more than 

 an optical effect arising from the fact that the inner cells are constricted 

 at regular intervals (29 — 1-3)- Wherever the constrictions meet the 

 side walls of the ceUs, these are here buttressed by props. In sections 

 the spaces between the constrictions are usually taken for single cells, 

 a mistake which I made myself at first. Within the central area 

 these lines, indicating the constrictions, run with great regularity from 

 cell to cell. In the region of the outer and lateral hinges they are 

 equally present, but are less regular. In the central hinge and in the 

 middle piece they are also present, but are here quite irregular and 

 numerous and are only with difficulty observable. 



The effect of these constrictions is to render the outer wall of the 

 inner course of cells readily compressible, like a bellows, without injury 

 to the cells. Without them it is hard to see how so great flexibility of 

 the door tissues combined with firmness and quick reaction could be 

 attained. It is indeed, as Meierhofer exclaimed, a "most wonder- 

 ful" arrangement. In the upper hinge the constrictions are not so 

 deep as in the middle area but are more numerous, which may be a 

 better arrangement for the maximum bending which this has to en- 

 dure. 



It may be pointed out that these cells have been represented (by 

 Ekambaram and Meierhofer) as having their anticlinal walls con- 

 stricted like the periclinal. This is not the case. It is true that if a 

 door is torn from its moorings and laid in water for examination the 

 injured cells along the torn edge will collapse and their uninjured 

 neighbors will swell and present the picture recorded by these authors 

 {24 — 9). But this cannot occur when the door is in situ and un- 

 injured. 



We now consider (a) the way in which the door edge lies in con- 

 tact with the threshold, so that it can maintain its posture in spite of 



