358 BOTANICAL GAZETTE [NOVEMBER 
another. It will be seen, however, that in every case the figures 
fall within the recognized experimental error. 
TABLE IV 
RESULTS IN RHIZOPUS NIGRICANS WITH TURNIP JUICE AND PLAIN AGAR; YOUNG STAGES 
GROWTH 
Number of : Number of| Total 
Nature of films and prepara- _Period of Average spores per | number | Percentage 
location of spores tions _|incubation| length of mm. = of hyphae | of reaction 
ined | in hours | hyphae in Pig rs Aseer counted 
er ages plain - 6.75 40 37 ran +2* 2 
A 2 | 7.25 66 58 168 | +18 / 
ower film: turnip ny 
juice agar+spores = 8.00 ane 56 192 +43 
ean = 
be sass urnip 2 6.75 75 53 189 +94 
B ae 2 7.25 136 49 206 +99 
L : plai 
pea <stiongpe 2 8.00 142. 46 198 +94 
(Upper film: turnip above 60} 20 179 =Ahe 
juice agar-++spores 2 6.75 below 51 15 mr +17 
Cc {above 80) 23 158 ——- 
2 .2 
ey (p00 1155 \Selow 58] 23 155 +33 
wer film: p ae 
\ agar-+spores 2 8.00 above 175 23 _ a 
below 148} 33 223 | +46 
ig film: turnip above 60| 21 272 ee 
juice agar+spores 4 7.00 below 74 27 292 +0.5 
wer film: oe above 80] 23 286. | —6.5 
uice agar-++spores : 
: . nes . ee below r1o1 22 378 —2.0 
Seite neice 
* +-and — signs indicate turning toward or away from the holes, that is, positive and negative 
reactions respectively. 
The most marked turning is shown in B, where the hyphae while 
still very short (75 «) show 94 per cent of reaction. Here we have 
both chemotropic forces exerting a stimulus in the same direction. 
A most interesting contrast to this is shown in A, where the turning 
is toward a plain agar film without spores. The turning is much 
less marked than in B, not in any case even half as great. The 
hyphae, indeed, are shorter, but this is balanced by the fact that 
on the whole the spore number, and consequently the number of 
hyphae, is greater. The result here, therefore, corresponds with the 
case of A among the older preparations described above, and 
the same observations apply here. Also, as would be expected in 
