406 Proceedings of Royal Society of Edinhurgh. [june 18 ’ 
Dr Frank (Botan. Zeitung^ 1879) in the root-fungus of the 
Leguminos 80 . 
The protoplasm of the nodular cells after a time becomes 
vacuolated (fig. 5) and filled with spores, which have been produced 
from the hyphse. At the same time the nucleus of the cell (which 
is stained a greenish-blue by acetic methyl green) is driven against 
the cell- wall (fig. 5), and degenerates to an oily globule easily stained 
black by osmic acid, and is dissolved by either chloroform or ether. 
These oily globules ultimately disintegrate and become mixed with 
the remaining protoplasm. Is it possible that the fungus has 
extracted from the nucleus some nitrogenous organic compound for 
its own nourishment, and that the oil globules represent the 
residue from the albuminoid molecules (C^ 2 ®ii 2 ^i 8 ®^ 22 ) 
nucleus that have suffered decomposition ? The spores of the said 
fungus are very minute (fig. 3) and are shaped like the letter V. 
From many points already considered in this paper, it is most 
likely that the cucumber-root fungus is one of the Dstilaginese, 
although there appear to be no transverse septa in the hyphal fila- 
ments of this fungus. There is little doubt that it is a modified 
form of the ordinary Ustilaginese. Modified most likely according 
to the surroundings of its life-history, which may be different in the 
host-plant, a member of the Cucurbitaceae, instead of the Graminese 
or the Leguminosae, whose genera are principally attacked by the 
Ustilagineae. We know from the writings of Alphonse De Candolle 
{Origin of Cultivated Plants, p. 265) that Cucumis sativa is an old 
form, having been “ cultivated in India for at least three thousand 
years.” It was introduced into Europe by the Greeks, and cultivated 
luxuriantly by them under the name of silmos (Theophrastus, Hist., 
lib. vii. cap. 4). The life-history of the cucumber (whose original 
habitat was in the region of Afghanistan) may have so considerably 
altered in its march towards western Europe that eveu the 
vegetable parasite, of which it forms the host-plant, may have 
undergone those changes in its internal structure already alluded to 
in this paper. 
Is not this an example of the Laws of Variation and the “ effects 
of changed conditions'^ ? In the words of Darwin {Origin of Species, 
chap. V.) : — “ I have shown that changed conditions act in two ways, 
directly on the whole organisation or on certain parts alone, and in- 
