Study of Spirogyra nitida. 239 



seven davs because of the attack of a fungus, which pene- 

 trated ami completely demolished the cell contents. Soon 

 after the formation of a large quantity of sugar, and the 

 Lengthening of the cell, the presence of this fungoid growth 

 could be detected. The conditions in the cell were favor- 

 able for its rapid growth, namely, a large quantity of soluble 

 nutritive substance, with a lowered vitality, which per- 

 mitted the inroads of organisms. 



Some investigators, notably Pfefifer, consider the yellow- 

 rays most active in causing assimilation. Judging from 

 the experiments just cited, the energy expended in the cell 

 is, indeed, great, but the ultimate growth is very abnormal, 

 there being a tendency toward an extensive production of 

 carbohydrate in a soluble condition. Is this energy such 

 that sugar can be produced in the cell without the appear- 

 ance, so far as micro-chemical tests can show, of starch ? 

 If so, starch-free cells placed for a time under yellow light 

 should have the sugar content increased. After this stage 

 their behaviour should correspond with that described in 

 the previous experiment. 



This was found by experiment to be perfectly true. De- 

 starched threads placed under the yellow screen were exam- 

 ined after 24 hours, but no starch had been produced, and 

 the quantity of sugar was not excessive. The cells were 

 of the usual length. Forty-eight hours showed the cells 

 much lengthened, and the sugar content was also greater. 

 On the fourth day the cells had attained to their full length, 

 they contained much sugar, and many of them had been 

 attacked by the fungoid growth. In control experiments, 

 destarched material when placed in white light, showed 

 always a prompt starch formation, and made a good growth. 



Orange.— Though following so closely upon one another 

 as do the orange and yellow rays, indeed slightly over- 

 lapping in the experiments herein described, the results of 

 their separate action are widely different. The narrowness 

 of these bands makes their dissimilar actions all the more 

 striking. 



