Francis E. Lloyd — 194 — Carnivorous Plants 



If closure follows trapping of suitable prey, narrowing (in the 

 sense of Ashida) takes place. Reopening follows at the end of a 

 period of days (5-10 or more) when there is evident a diminution of 

 sensitivity, which however is regained in the course of time (some 

 days, OuDEMANs). 



Digestion. — During all this digestion and absorption have been 

 taking place. Darwin did a variety of experiments with various 

 substances. We have seen that the upper surface of the lobes is 

 crowded with many glands capable of secretion and absorption, as 

 Darwin stated. These glands remain passive unless some suitable 

 material (insect, meat, etc.) is inclosed between the lobes. Then 

 there is a copious secretion of a fluid which has the power of diges- 

 tion, and which causes the dissolution of the substances acted upon. 

 "It is so copious that on one occasion, when a leaf was cut open, 

 on which a small cube of albumen had been placed 48 hours before, 

 drops rolled off the leaf" (Darwin). The secretion is acid, the pres- 

 ence of formic acid (Balfour) serving also for the inhibition of bac- 

 teria, so that, unless too great ''portions" have been supplied, there 

 is no odor of decay. Balfour found that a strip of meat placed partly 

 within the closed valves and partly out, showed no bacterial action 

 within, but did so without. When the rotted portion was placed in 

 a fresh leaf, the odor of decay disappeared. This contravened the 

 opinion of Rees and Will, whose experiment seems to have been done 

 with abnormal plants (Goebel). There seems therefore to be no 

 doubt of the digestive power of the secretion, though no in vitro 

 experiments have been done with Dionaea secretion. According to 

 Darwin some substances are not digested (fats, iibro-elastic cartilage). 



If not too great masses of material have been fed, when the trap 

 begins to open the interior is found to be dry, and the fluid has been 

 entirely absorbed. Experiments to show the usefulness of the ab- 

 sorption of proteins, such as those carried out by various authors on 

 Drosera, Utricularia, have not been done. Our opinion on that must 

 therefore rest on evident analogy. 



Fraustadt thought that during the period when the trap is closed 

 over an insect photosynthesis stops. But Pfeffer (1877) suggested 

 that the lowering of the starch content observed by Fraustadt may 

 be the accompaniment of a change in metabolism while at the same 

 time photosynthesis may be proceeding. The work of Kostytschew, 

 if meagre, seems to deny Fraustadt' s belief (see under Drosera, 

 p. 119). 



Aldrovanda vesiculosa L. : — Aldrovanda is a small fresh water plant 

 {ly — 5) growing in quiet waters, floating just below the surface. 

 It is quite rootless, and consists of a slender stem, clothed with whorls 

 of leaves not distantly separated. Each whorl has eight leaves mu- 

 tually attached at their bases. It branches infrequently, so that usu- 

 ally one finds only a single stem. The whole plant reaches a length 

 of 10 to 15 cm. with a width of 2 cm. including the spread leaves 

 which are refiexed in age. The tip of the shoot is especially con- 

 spicuous by the numerous bristles which jut beyond the general leaf 

 profile. The flowers are supported on short stalks, bringing them 



