Physiology of the Genus Cuscuta. 81 
localization in the more superficial and hence better illuminated 
cell-layers, rather than in the central and comparatively dark 
tissues, confirms the opinion that they are functional. I have 
not attempted any chemical experiments to determine the 
amount of oxygen evolved. It is to be noticed further that 
if, instead of cutting off only about six centimetres of the tip 
of each branch, the cutting be ten or more centimetres long, 
there is less development of chlorophyll and more growth 
in thickness of those parts which have coiled closely around 
the host ; and that, as the root and the lower parts of the 
stem of the seedling yielded the nutrient matters which they 
contained to the younger upper parts and died, so the lower 
parts of the cuttings decrease in size, shrivel, and die. 
Evidently their substance is taken away and consumed by 
the younger coiling parts. But as the preceding experi- 
ments show, no matter how much nourishment the part 
which is forming haustoria can secure from the other parts of 
the parasite, this is sufficient only for the growth in thickness 
which normally accompanies the formation of close turns 
around the host, and to forestall the necessity of developing 
chlorophyll-granules ; it is not sufficient for the full develop- 
ment of the epidermal prehaustoria and of the haustoria 
proper. 
The development of chlorophyll in these parasites is always 
a consequence of insufficient food, as the following experi- 
ments indicate. I raised three sets of C. Epilinum on the 
common Flax under various conditions. One set was raised in 
a suitable bed out of doors, the seeds of host and parasite 
being sown together. The Flax-seeds germinated first, and 
the young plants were growing vigorously when attacked by 
the seedlings of the Cuscuta. From the same lots of seeds 
I sowed still more simultaneously in pots of moist earth in 
a dry and rather cool greenhouse. After the seedlings of 
Flax and Dodder were well started, I brought half the pots 
into the laboratory, setting them on a window-sill. The other 
half I left in the greenhouse. The air of the laboratory, 
though somewhat warmer than that of the greenhouse, was 
G 
