Francis E. Lloyd — 200 — Carnivorous Plants 



and more scattered nearer the midrib, on which, however, there is a 

 dense row of them. Darwin regarded the "quadrifid" or cruciform 

 hairs within the trap as absorptive, but Duval-Jouve (1876), because 

 of their occurrence on the outer surfaces of the petiole, etc., considered 

 them as of identical nature with the latter. 



In this region, to which, thought Mori (1876), irritability was con- 

 fined, there are also about 40 (20 on each lobe) long, very slender hairs, 

 described by Goebel, Haberlandt and Fenner, analogous to the 

 normally six sensitive bristles which occur on the lobes of the Dionaea 

 trap. In Aldrovanda, however, they are of a much simpler though 

 equally effective structure. They are about 1.3 to 1.5 mm. long and 

 0.05 mm. thick except at the base, where they are a bit wider. ^ They 

 are very slender shafts, arising from a four-celled base lying in the 

 epiderm, and projecting slightly therefrom. On these is surmounted a 

 length of two courses, each of four long, slender cells. These bear the 

 super-sensitive cells, four in number, though sometimes there appear to 

 be only two. Haberlandt does not state the number. They are 

 short, thin-walled and form a sort of joint or hinge where the otherwise 

 stiff hair can bend sharply, thereby compressing the cells on the con- 

 cave side (Goebel, 1891). Above there are two courses of slender cells 

 of two each, gradually tapering to a sharp, sometimes forked, end 

 (ig — 20). They are arranged and postured in such fashion that, 

 contrary to the impression given by some authors, they are not bent on 

 the closure of the trap. They stand upright on the flat region of the 

 trap on either side of the midrib, where they have plenty of head-room 

 when the trap is fully closed, but obliquely on the sides so that, though 

 long enough to reach beyond the fully closed digestion chamber, they 

 lie sandwiched between the thin regions when approximated without 

 being bent. Disturbing these hairs results in the closure of the trap, 

 one touch of a bristle of a young leaf sufficing, but as the leaf grows 

 older two or even many more become necessary. Quite old leaves, 

 appearing at first to be beyond response, showed action when a lot of 

 the sensitive hairs were disturbed by a sweeping motion of a needle a 

 considerable number of times. 



But though I did 300 experiments I found it diihcult to make a 

 very definite rule. There is a good deal of difficulty, of course, in 

 getting a clear-cut result when one is dealing with so small an object 

 as the Aldrovanda trap which has so many deHcate bristles close to- 

 gether. In cases where the results were quite clear-cut, the data 

 were contradictory. Thus in one case a young trap responded to 

 one touch of a single hair while another one, of similar age and ap- 

 parently ready for action, being widely open, required seven stimuh 

 appKed to a single bristle. Another required even more, caused by 

 a sweeping of a number of hairs after six single stimuH. In some- 

 what older leaves, two stimuh only were frequently required to effect 

 closure, but this also was by no means constant. Older traps behaved 

 often in a singularly refractive fashion, but yet were found to respond 

 at last. One case only: a single inner (on the fiat region) bristle 

 was bent 10 times; a second was bent 10 times; several bristles 

 were then bent by a sweeping motion 10 times; then several outer 

 bristles were swept ten times, and finally a single inner bristle was 



