718 The American Naturalist. ; August, 
legnia ferax. Subsequently he also experimented with Botrytis bas- 
siana, B. tenella, Uredo linearis and with the pollen of Digitalis 
purpurea and of some other Dicotyledons, the results being much the 
same except that they are attracted by fewer substances. In brief, 
he finds the germ tubes of the species experimented on to be indiffer- 
ent to some substances, to be repulsed by others, and to be strongly 
attracted by still others. In some cases the attraction is so strong that 
an indifferent fungus-like Penicillium is converted into an active para- 
site by simply injecting the living leaves on which the spores are sown 
with a dilute solution of the attractive substance, e. g., 2 per cent. cane 
sugar. The germ tubes bore through the epidermis or enter at the 
stomata and ramify through the interior of the leaf, boring through 
cells as well as passing between them, while they show no tendency to 
enter leaves injected simply with water. The suggestiveness of this sort 
of an experiment is certainly very great. The spores were separated 
from the chemotropic substance by films of mica or collodium perfor- 
ated with fine needle punctures, or by means of the epidermis of vari- 
ous plants. Without entering into details, some of the main conclu- 
sions reached by Mr. Miyoshi may be summed up in the following dia- 
grams which I have prepared from his tables. These experiments 
were made with layers of gelatin separated by thin films of collodium 
containing fine needle punctures. The interrupted horizontal lines 
represent collodium membranes separating layers of 5 per cent. gelatin, 
previously washed in HCl to remove the disturbing, nutrient lime salts. 
The dotted areas indicate the particular layer of gelatin containing the 
spores to be tested. The diagonally shaded areas indicate the layers 
of gelatin to which the chemotropic substance was added, in these cases 
2 per cent. cane sugar. The vertical lines represent the walls of the 
glass dishes. The arrows indicate the direction of the movement of the 
germ tubes when there was marked chemotropism. Zero denotes that 
there was no movement of the germ tubes into the compartment, and 
* indicates that the germ tubes grew indifferently in all directions. In 
the first diagram the experiments were with Phycomyces nitens and 
Mucor stolonifer, in the second with M. stolonifer. 
