INFLUENCE OF CHEMICAL STIMULATION 63 



98. Chemotropic Reactions of Mucor or other Moulds to Sugars. 

 Prepare a two per-cent. solution of cane sugar and place a leaf of 

 Tradescantia in it. Set on the plate of an air pump, and cover 

 with a small receiver. Exhaust the receiver. This will draw the 

 air from the leaf and inject the intercellular spaces with sugar. 

 Remove the leaf, wash quickly in water and wipe dry. Place the 

 leaf with the under side uppermost on a plate in a moist chamber. 

 Now sow spores of mould on the leaf. Examine daily with the 

 low power of the microscope and note direction taken by the 

 hyphae formed by the germination of the spores. 1 



99. Influence of Chemical Stimulation upon Developmental Proc- 

 esses. Chemical substances in the medium in which an organism 

 lives may affect the growth and development of various organs in 

 many ways. The stature and form of the organs, the structure 

 of the tissues, the rate and amount of growth, and the perform- 

 ance of reproduction may be profoundly modified by the presence 

 or absence of chemical agents, in a relation wholly due to a stimu- 

 lating effect, and entirely beyond their nutritive or trophic value. 



Richards has found that such substances as sodium fluoride, 

 zinc sulphate, sodium silicate, cobalt sulphate, cocaine, and mor- 

 phine in minute quantities cause an acceleration of growth both 

 as to rate and ultimate performance in various fungi. Schulze 

 found that such substances as corrosive sublimate, iodine, bro- 

 mine, and arsenious acid increase the activities of yeast in fer- 

 mentation. Ono traced the influence of various salts upon algae 

 and fungi, and many investigations upon the subject are cur- 

 rent. 2 



1 Molisch. Zur Physiologic des Pollens mil besonderer Riicksicht auf die chemo- 

 tropischen Bewegungen der Pollenschlauche. Sitzungsb. d. Akad. d. Wiss. Wien. 

 102; 423. 



Miyoshi, M. Ueber chemotropismus der Pilze. Bot. Zeitung. 52. I. 1894. 



2 Richards, H. M. Die Beeinflussung des Wachstums einiger Pilze durch chem- 

 ischer Reize. Jahrb. Wiss. Bot. 30 : 665. 1897. And, The effect of chemical irri- 

 tation on the economic coefficient of sugar. Bull. Torr. Bot. Club, 26 : 463. 1899. 



Schulze, H. Ueber Hefegifte. Arch. f. Ges. Physiologic. 43: 517. 1888. 

 Ono, N. Jour. Coll. Science Imp. University, Tokyo. 13 : 143. 1900. 

 Clark, J. F. Dissociation and toxic effect. Journ. of Physical Chem. 3 : 263. 

 1899. 



