258 



STRUCTURE AND LIFE HISTORIES 



The protoplasm appears to be streaming in a constant 

 current in one direction, and this is thought to be due to 

 the evaporation of water from surfaces more exposed to 

 the air, and the intake of more water from the substratum, 

 by osmosis. 



FIG. 185. Bread mold (Rhizopus nigricans}. A, older plant; myc, 

 mycelia; sph, sporangiophore; sp, sporangium; st, stolon produced by .4, 

 and giving rise at its tip to a new plant, B. Greatly enlarged. 



261. Secretion of a Powerful Poison. In the course 

 of some experiments, made in order to determine the 

 cause of sex in the mucors, Blakeslee and Gortner in- 

 jected into the ear of a healthy rabbit some of the juice, 

 squeezed out of the mycelium of Rhizopus nigricans. 

 To their great surprise the animal died almost instantly, 

 before 'the injection was completed. Further experi- 

 ments clearly demonstrated that Rhizopus contains a 

 powerful poison (or toxin), which is soluble in water, 

 but which produces its effect only when introduced into 

 the circulatory system. When this expressed juice was 

 fed to the rabbits, or when they ate the mycelium, no 



