254 Pennington — A C he mico- Physiological 



If protoplasmic activity depends upon the multiplication 

 of unstable nitrogen atoms the increased movement of the 

 protoplasmic pellicle may be due to the synthesis of such a 

 product under these abnormal conditions. 



By the time we reach the blue rays the diastatic activity 

 has greatly diminished. Yet enough energy still remains 

 to convert the starch grains, little by little, into soluble 

 products, though these seem to differ chemically from those 

 compounds generally obtained by diastatic action. The 

 cell energy, too, has fallen so low that carbon dioxide and 

 water are no longer decomposed to yield starch as the first 

 visible product. When the supply with which the cell 

 was furnished is used up, its resources are at an end and 

 death ensues. Under blue light we may say that meta- 

 bolism is at a minimum, while carbon dioxide assimilation, 

 so far as we can determine, has ceased. The density of the 

 protoplasm shows that a very pronounced alteration has 

 taken place in its composition, and this is shown likewise 

 by the color which iodine imparts to it. This color would 

 indicate that even though the starch is slowly hydrated the 

 energy is not sufficient to carry it to a true sugar, and can- 

 not link together nitrogenous and carbohydrate substances 

 into the proteid found in the plant under white light. 



The violet screen, which furnishes the more refrangible 

 rays, does not seem capable of changing the starch which 

 is already in the cell, into any product which can be used 

 in plant metabolism, though it is indeed somewhat altered, 

 since we find a blue color diffused through the cell after 

 treatment with iodine. Probably both this fact and that of 

 the greatly reduced cell energy combine to produce a con- 

 dition in which proteid cannot be formed in Spirogyra. 

 This same energy, on the other hand, is not only sufficient 

 for, but favorable to, the growth of certain bacterial organ- 

 isms. The deleterious effects of this screen are seen also 

 in the action of diastase on starch where the time required 

 for hydration is twice as long as the time required when 

 white light acts. 



