54 PLANT PHYSIOLOGY 



185, 11. 2-10, for As yet . . . exist in them read The secretions appear frequently 

 to have antiseptic properties, so that the co-operation of Bacteria in the diges- 

 tion of the insects is excluded from consideration. 



In Drosera the peculiar tentacles which arise from the lamina are tipped 

 with glands which always give off a slimy substance, which by its stickiness 

 holds the insect fast. When the glands are stimulated, however, by the presence 

 of a nitrogenous organic substance a very copious secretion begins, and it 

 can be shown that this secretion has an acid reaction and contains an enzyme. 

 The latter has for long been recognized in glycerine extracts of the leaves. 

 Glands similar to those of Drosera are met with in Drosophyllum, but only some 

 of them are at the ends of tentacles ; the majority are sessile on the leaf surface. 

 It would appear that in this case only the sessile glands furnish the acid fer- 

 mentative secretion, and this secretion begins only after the stalked glands 

 have been stimulated chemically (FENNER, 1904). 



The arrangements are essentially different in Dionaea. In the unstimu- 

 lated condition the leaf is dry, and the sessile glands, which resemble those 

 of Drosophyllum, give off their fermentative and acid secretion only after 

 stimulation effected by the entrapped insect, but then in such quantity that 

 it trickles away from between the closed halves of the leaf-blades. 



Finally, in Nepenthes, the young pitcher secretes a slimy, tasteless fluid, 

 giving a neutral reaction. This reaction becomes acid after stimulation, 

 whether the stimulus be mechanical or chemical ; after that, the secretion is 

 in a condition to act digestively. According to CLAUTRIAU'S researches (1900) 

 in the woods of Java, the absorption of proteid takes place extremely rapidly, 

 and apparently without any very profound decomposition. On the other hand, 

 according to VINES (1897-1902, 1906), in addition to a vigorous peptic enzyme, 

 a more feebly active erepsin is secreted which decomposes the peptone formed 

 by the peptic enzyme. 



Whether these two enzymes are always distinguishable in carnivorous 

 plants it is impossible to say ; nor is the evidence conclusive with regard to 

 the nature of the acids which are always present. Often it is formic acid that 

 is recorded, but propionic, butyric, and other fatty acids have also been found, 

 while nothing is known as to the occurrence of inorganic acids. These latter 

 are not unlikely, seeing that in the animal hydrochloric acid is produced for 

 a similar purpose. 



1. 16, after three days, read In other cases, e.g. in Drosophyllum and 

 Nepenthes, this process must take place much more rapidly ; but comparative 

 experiments on the subject are entirely wanting, and the chemical peculiarities 

 of carnivorous plants in general, without doubt, deserve fresh and thorough 

 investigation. 



186, 1. 19, for soil only. It is even read soil only ; it would appear also that 

 the root system of carnivorous plants is only moderately developed. It is 

 even 



1. 25, for perfectly obvious read exceedingly probable 



187, 11. 36-43, for although isolated . . . history read although it contains 

 chlorophyll. The amount of chlorophyll in Cuscuta varies. According to 

 PIERCE (1894) an increase in chlorophyll occurs in amputated shoots ; but 

 according to a manuscript communication from PROFESSOR NOLL it is prob- 

 able that this depends more on diminished intensity of light than on mere 

 isolation. It may be assumed that the chlorophyll is functional, but that the 

 products of assimilation are insufficient in quantity to maintain the plant in 

 life. We must look upon the capacity for forming chlorophyll as an indica- 

 tion that Cuscuta has been evolved from chlorophyll-bearing plants ; possibly, 

 like Lathraea, it may in time entirely lose its power of forming chlorophyll. 



