GILBERT M. SMITH VH 



of sexual substances in the Stanford series, but in darkness these sub- 

 stances do diffuse from the cells at a much slower rate. 



Unpublished results of studies by H. C, Wendlandt at Stanford 

 show that there is a quantitative relationship between white light from 

 a fluorescent lamp and the development of sexual substances by C. 

 Reinhardi. This was done by comparing the time required for the 

 appearance of sexuality in cultures grown in darkness and then exposed 

 to white light of i, lo, 25, and 50 foot-candles' intensity. The time for 

 development of sexuality is not the same in all cultures exposed to light 

 of any given intensity, but when the average time is taken for experi- 

 ments in sextuplicate at each intensity the results are consistent (Table 

 4). There is no appearance of sexuality in cultures illuminated at i foot- 



TABLE 4 

 Average number of minutes exposure to white light of increasing intensity re- 

 quired for appearance of sexuality in cultures of plus strains of Chlamydomonas 

 Reinhardi grown in darkness when mixed with sexually functional minus cells 



candle, even if this is continued for more than 224 hours. In the other 

 light intensities the time interval for the formation of sexual substances 

 decreases as intensity of illumination is increased, and for each intensity 

 there is a progressive strengthening of the sexual reaction as illumination 

 is continued. Differences in time for sexual substances in plus and minus 

 strains of C. Reinhardi are insignificant. 



The effect of light of different wave lengths upon the formation of 

 sexual substances has also been studied in various members of the 

 Stanford series. This was done by pouring nutrient agar into Petri 

 dishes, allowing it to gel, inoculating the surface with material from a 

 culture grown in light, and culturing for two weeks in blue light 

 (4357 A) and in red light (6150-6900 A). When these palmella cultures 

 were taken to the dark room and flooded the cells became motile and 



