GRAVES: CHEMOTROPIC REACTIONS IN RHIZOPUS 



327 



going into detail, it was clear from the fact that the hyphae are 

 continually producing a staling substance, that the number of 

 spores and the length of the hyphae must be taken into account 

 in experimental work on positive chemotropism. In the ex- 

 periments with agar with fresh turnip juice added, the first 

 definite indication of a positive chemotropism — working, it is 

 true, side by side with the negative chemotropism — was obtained. 

 The hyphae grew much more vigorously in the turnip juice medium 

 than in sugar media. They did not in all cases grow faster: the 

 chief difference consisted in the thickness of the germ tubes, which 

 were twice or three times as thick as when grown in glucose or 

 cane sugar agar. Probably on account of this healthier develop- 

 ment they reacted much better to chemotropic influences than 

 when grown in the sugars. 



Combinations of spores and medium were tried with results such 

 as shown in the following table. The arrangement of films and 

 spores in each combination — the latter denoted by a large letter^ — 

 is shown in the first column. Here the mica plate Is represented 

 by the short line separating the two films, with their composition 

 and the location of spores in them as stated. 



Table I 



Turnip-juice agar 



Turnip-juice agar 



4- spores 



100% 



(noticeable three diameters 



from hole) 



The turning toward the holes in B and C was most remarkable, 

 but in A was not nearly so pronounced. The only difference 

 between B and C lay in the distance from the hole at which the 

 turning became noticeable. In the same period of time. In C, the 

 reaction was apparent at a distance of from three to four diameters 

 of the hole, counting from its margin. But in B, the turning 

 could be observed as far as ten diameters from the hole. In B 



