102 BOTANICAL GAZETTE [FEBRUARY 
the surrounding atmosphere, as was apparent from the dry condition 
of the gelatin around the holes in the uppermost plate; water diffused 
from the lower layers to supply the deficiency. In this way it came 
about that the middle layer, which contained the spores, was moister 
than the uppermost layer, but drier than the lowermost. There was 
observed a very decided turning of the hyphae toward and through 
the openings in the third plate, which separated the middle and 
lowermost layers, while comparatively few grew toward the upper- 
most layer. The estimated percentages are shown in Table IX. 
TABLE IX 
= 
< 4s = a “| a 
< n 2 
S8/S2/$2)Ee| 88/68) 38| 8 ge 
DrrEcTIONs PO|Bo|s4|/eea1f5/2#/8e|82)| 28 
z Ze|°o iH < blagipYipdl ge 
S0).09)3n/80) 82) a2 seisei se 
AB\SE/BR/RB| Ae/Be |" 4/28 | BA 
& = ae > a a a) ey 
From middle layer to lowermost layer..| 43 | 70 | 80 | 55 | 68 | 65 | 73 | 63 | 65 
From middle layer to uppermost layer..| 20 | 20 | 20 | 30 | 18 | 15 | 18 | 1 18 
Experiments were set up in which very firm gelatin (16 per cent.) 
containing the spores was covered with mica plates having a few 
perforations. The plates were sealed to the covers by an application 
of vaseline around their margins.. The covers were then inverted 
over stender dishes level full of sterile distilled water. In this way 
the water came in contact with the gelatin only through the perfora- 
tions, and diffused from these through the gelatin layer. Hyphae 
of Mucor stolonifer grown under these conditions showed a tendency 
to grow toward the openings from a distance of 1.5™™, but on coming 
within 0.5™™ of the openings, the course was changed, and the 
hyphae circled the openings in lines more or less concentric with 
their margins. The majority of those nearer the openings than 
0.5™™ grew in a radial direction away from them. Ina few instances 
hyphae grew into the water. Mucor mucedo showed a quite decided 
turning toward the holes, and about 65 per cent of the hyphae within 
a radius of three hole-diameters turned through them and grew into 
the water. With Botrytis vulgaris about 40 per cent., and with 
Penicillium glaucum 85 per cent. of the hyphae within a correspond- 
ing area were affected positively. In every case the growth 
