4 HOOKER: PHYSIOLOGICAL OBSERVATIONS 
atmosphere, without being fed with insects. They lost all traces 
of pigment. Six of these were fed with small flies and two days © 
later pigment was observed in the marginal tentacles of the 
_ youngest leaves, that had just unrolled. A similar reappearance 4 
of color was observed in three other plants which caught insects. 
This is the opposite of the results obtained by F. Darwin (’08, 
p. 23) and by Biisgen (’83, p. 592), who found that plants fed with 
insects had much greener leaves than those which relied solely on — 
photosynthesis for their nourishment. The contradiction may ~ 
be owing to different environmental conditions, such as the 
chemical composition of the substrate, the intensity of the light, 
or the humidity of the atmosphere. The question merits further 
investigation. 
4. HABIT 
Another peculiarity observed in plants cultivated in a moist 
atmosphere was the peculiar habit assumed by the plant. The | 
internodes became lengthened, and this was the case with plants — 
exposed either to the diffuse light of the laboratory or to direct sun- _ 
light. Plants exposed to dry air were observed to retain the rosette — 
habit under both light conditions. This shows that the rosette 
habit characteristic of D. rotundifolia is dependent upon transpira- _ 
tion and not upon light, as Diels (’06, p. 32) suggests. This rela- 
tion represents an interesting adaptation, for as long as the plant is 
beneath the surface, the internodes lengthen, since transpiration 
is reduced toa minimum. In this way the terminal bud is brought 
to the surface, where rapid transpiration from the exposed leaves 
causes the development of a rosette. 
5. PARASITES 
A great many of the plants cultivated in the laboratory were 
destroyed by larvae actidentally brought with the material from 
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the swamp. They were larvae of one of the cut-leaf moths or | 
noctuids. Since the adult form has not been obtained, it has — 
been as yet impossible to identify them. The young larvae are © 
about a quarter of an inch long and very pale. They climb up 
the under side of the leaf-petioles and eat the blade from behind. 
In this way they avoid the tentacles which could easily catch and 
digest ‘such small creatures. The larvae select the youngest 
