Physiology of the Genus Guscuta. 57 
in older plants I shall have more to say further on.) The 
stem being now erect or nearly so, and continuing to grow in 
length, nutates in wider and wider circles or ellipses in search 
of some suitable object around which to twine. As first 
pointed out by Von Mohl *, the seedling will not twine indis- 
criminately about any object whose size, form, and position 
one might suppose to be appropriate, if not directly to nourish, 
at least to hold it up in its efforts to reach a nutrient support, 
namely some living plant. Von Mohl tested this by pieces of 
wire and thin rods of fir-wood kept for three days in contact 
with the seedling. The plant refused to twine about them, 
though, when brought into contact with a plant of Nettle, it 
wound about it within nine hours. Koch 1 2 and others have 
confirmed this important observation, but without being able 
to account for the fact. Koch 3 says — ‘ Der junge Schmarotzer 
besitzt somit in Bezug auf den von ihm zu befallenden Gegen- 
stand eine gewisse Wahlfahigkeit, deren physiologischer 
Nutzen nicht zu verkennen ist.’ 
Through the integuments of the seed the embryo receives 
from the moist soil, or damp substratum of any sort on which 
the seed may rest, sufficient water to cause it to germinate, 
other conditions of temperature, &c., being favourable. The 
spindle-shaped and but feebly-developed root continues to 
secure moisture through its hairs from the substratum, and 
thus provides the necessary amount of water for the solution 
and transportation of the food-substances stored in the endo- 
sperm. The root is, however, a short-lived structure, begin- 
ning to die generally within seven days after its appearance, 
and hence it can supply only a small quantity of water in all. 
Under favourable conditions, primarily a damp substratum 
and a moist atmosphere, the root doubtless supplies enough 
water completely to convert the reserve food-materials in the 
endosperm into transportable and available solutions ; but 
if, owing to the surrounding air being dry, the transpiration of 
1 Mohl, H. v., loc. cit. 
2 Koch, L., Hanstein’s Botanische Abhandlungen, Bd. II, Heft 3, p. no, 1874. 
3 Koch, L., Die Klee- und Flachsseide, Heidelberg, 1880, p. 17. 
