Francis E. Lloyd — 192 — Carnivorous Plants 



the application of a plasmolyte to the upper surface, no closure can 

 take place on stimulation (application of the plasmolyte to the base 

 of the sensitive hairs was avoided). Indeed, any experiment in which 

 the parenchyma is robbed of its turgor renders the valves incapable 

 of closure. This positive drag therefore, present before closure, 

 stretches the epiderms as much as it, previous to excitation, is ca- 

 pable. On stimulation this capacity is increased, the epiderms re- 

 sponding by expanding differentially, the upper scarcely at all, the 

 lower 6-7%, in accordance also with measurements by Brov^n and 

 others. Von Guttenberg then faces the questions, whence the water 

 necessary to increase the volume of the parenchyma cells, and what 

 conditions allow the momentary increase of water uptake? To the 

 former he suggests that the water comes from the vascular tissues; 

 to the latter that it may be due to the sudden changes of substances 

 in the sap from a large molecular to a small molecular condition. 

 Von Guttenberg extends this theory to the case of Aldrovanda, 

 making the pertinent observation that, in view of the fact that this 

 trap has only a single course of parenchyma cells, it is unthinkable 

 that there exists a differential action in the tissues between the epi- 

 derms, of which more beyond. 



Von Guttenberg's difficulties may, however, on theoretical grounds 

 be avoided. If it be assumed that the response to irritability is con- 

 fined to the epidermis, we might argue that this response consists 

 only in the reduction of turgor. True, as von Guttenberg says, 

 this would be removing one factor in tissue stretching, but as turgor 

 expands the cells in every direction, the relative amount of exten- 

 sion depending on the lengths of the walls, its removal would allow 

 the application of the energy of the turgid parenchyma to the flaccid 

 epidermal cells, the longitudinal walls of which then would respond 

 readily to the stretching effort, the amount of stretching depending 

 only on the physical properties of the walls. In a word, the system 

 would work like a bimetalhc strip of metals of different indices of 

 expansion, von Guttenberg's idea, but demanding simply loss of tur- 

 gor in the epidermis only, and this, as von Guttenberg observes in 

 regard to Ziegenspeck's theory, is easier physiologically than a rise 

 in turgor in a mass of tissue. It should be added that the loss of 

 turgor by the epidermis need not advance beyond an initial stage 

 of relaxation, just sufficient to allow, without evident effusion of water, 

 the stretching of the longer walls, which would otherwise be pushed 

 out laterally by conditions of turgor. Thus the theoretical neces- 

 sities are reduced to a minimum, and the movement of Dionaea 

 brought into fine with movements in general in sensitive plants. 

 As to the bursting of fruits such as Impatiens, Sicyos, etc. we have 

 to do with change of shape of parenchyma cells without change in 

 turgor. In Impatiens the two epiderms are of unequal extensibility. 



This seems to be the view advanced by Ashida (1934) which, 

 prompted by his study of Aldrovanda, he applies "by deduction to 

 the case of Dionaea." He cites Macfarlane's observations that 

 the lower epidermis has a thinner cuticle than the upper, and is there- 

 fore more easily distensible, permitting curvature on the relaxation of 

 the upper epidermis with the effect of closure. 



