84 LON A. HAWKINS 



be without apparent effect; under such treatments the spores germinate 

 normally within eighteen hours, just as they do in the control with dis- 

 tilled water. (2) Germinal activity may be manifest, but in other ways 

 than that which is here considered as normal. Under treatments which 

 produce this sort of response, the activities of the spores result sometimes 

 (a) in an actual decrease in the exposed surface as well as in the volume 

 of the organism, and sometimes (b) in an increase in both volume and 

 surface, the latter, however, increasing much less markedly, as related to 

 increase in volume, than is the case in normal germination. In the first 

 category (a, above) belong the phenomena involved in the production of 

 the dark bodies which have been described as forming within the spore wall 

 and occupying only a portion of its volume. These appear to have essen- 

 tially the characteristics of chlamydospores formed within the organism. 

 All other renewed activities of the spores which have been described belong 

 to the second category (b), and embrace those growth processes which 

 result in more or less restricted swellings, especially at the ends of the 

 spores, in appressoria, with either dark or hyaline wall, and in short germ 

 tubes somewhat resembling the normal tubes but of much greater diameter. 

 (3) No renewed activity may occur at all during a period of from eighteen 

 to twenty hours under the given treatment, although ability to germinate 

 if transferred from this treatment to another (as to distilled water) may 

 still be retained. Here the treatment prevents germinal activity but does 

 not destroy viability, at least within the given time limits. (4) Viability, 

 or power to germinate in water, may be destroyed within a period of from 

 eighteen to twenty-four hours; the organism is killed outright. 



It has already become clear in this work that most of the substances 

 dealt with produce death within the assumed time limits, if applied at a 

 sufficiently high concentration (4). With a somewhat lower concentration 

 of the injurious material, germination is inhibited but viability is retained 

 throughout the given period (3). When the concentration is still lower 

 germinal activity becomes manifest but takes other forms than those recog- 

 nized as normal (2). Finally, when the concentration of the toxic agent 

 is still further decreased, the stimulation threshold in the present sense is 

 passed and normal germination becomes the rule (i). 



Livingston 21 working with a green alga has presented a somewhat similar 

 series of responses to chemical stimuli. This writer studied the effect 

 of a large number of nitrates and sulphates on a form of Stigeoclonium, 

 adding different concentrations of the salts to a nutrient medium in which 

 the alga was grown. With a dilute nutrient solution, in which the alga 

 had a characteristic filamentous form, its response to stimulation might be 

 considered as of three types, (i) death, (2) change in phenomena of 



21 Livingston, B.E., Chemical stimulation of a green alga. Bull. Torr. Bot. Club 32: 1-34. 1905. 



