82. BOTANICAL GAZETTE [FEBRUARY 
WorTMANN (36) observed the turning of young germ-tubes of 
Saprolegnia sp., and concluded that these are very sensitive to chem- 
ical stimuli, especially to those concerned in nutrition; a most 
energetic turning was observed toward flies’ legs. 
MARSHALL WARD (32) mentions two factors as mainly influen- 
cing the direction of growth of “‘lily-botrytis,” namely, the contact of 
hyphae with one another or with solid bodies, and the direction in 
which food lies in relation to the growing hyphae. | 
Worontn (34) holds that it is through chemical influence that 
the conidial germ-tubes of Peziza baccarum reach the wounds of the 
host plant. 
STRANGE (29) made careful observations on growing hyphae of 
Saprolegnia ferax for the purpose ‘of confirming their reported turn- 
ing toward nutrient substances. That the hyphae turn toward a 
region of diffusing nutriment was regarded as very questionable; 
there was noticed, however, a stronger growth of the hyphae in the 
nutrient region, and the hyphae, by their branching, became more 
abundant here than elsewhere. The germinating conidia sent their 
tubes in all directions, provided enough nutriment for growth was 
present, and not markedly toward any area containing a greater 
amount of nutriment. Similar results were obtained with germ- 
tubes from Penicillium spores; these showed no chemotropic turn- 
ing, but a much better growth when they reached the diffusion 
region around the openings of the capillary tubes containing the 
test solutions. 
REINHARDT (28) found that the direction of growth in Peziza 
sp. is affected by chemical influences. Gelatin containing sugar and 
spores of Mucor sp. have an attractive effect. Spores of Aspergillus 
niger, A. flavus, and Penicillium glaucum, as well as colonies of 
various bacteria, cause a cessation of growth, which is followed by a 
reversal of the direction of growth. 
BUSGEN (2) observed chemotropism in the case of Botrytis cinerea, 
and supposed that a chemical stimulus might cause the germ-tubes 
in the dew-drop to seek the host epidermis; but he considered that 
penetration is brought about by contact influence. He asserts the 
possibility of chemotropism in the case of germ-tubes from uredo- 
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