240 Pennington — A Clicmico-Pliysiological 



Two or three days under the yellow screen sufficed, as 

 we have seen, to free the cells from starch, fill them with 

 sugar, and in many ways alter what we would consider to 

 be distinctive characters. On the contrary, five days 

 under the orange made no appreciable differences. The 

 plant's behavior was normal. By the eighth day the 

 number of crystals had greatly diminished. The oxalate 

 crystals suffered more than did the tartrate, the former 

 almost entirely disappearing from the cells, while the 

 latter, though few in number, were in fairly good condition. 



An examination for sugar showed this substance to be in 

 larger quantity than in the control threads grown under 

 white light. However, it was still far below the quantity 

 of sugar contained in the culture made in yellow light. 



The protoplasmic pellicle w T as modified in that it had 

 lost its granular structure, and was clear and refractive, 

 though not so much so as in the case of the yellow. The 

 nucleus and its threads partook of this change also. The 

 nucleus stood out clearly in the cell, while the nucleolus 

 was very large and prominent. No change in shape or in 

 the relative positions of these bodies could be observed. 



Tannin was always present, and in fairly large amount. 

 Its quantity varied without recognizable cause, just as it 

 does when the plant is exposed to white light. 



Occasionally cells were seen which were longer than the 

 normal. These were not very frequent, and were not more 

 than twice the length of the other cells. 



The cultures in orange light were sometimes kept under 

 observation for five weeks. At the end of this time they 

 were still healthy, showed very few crystals, contained 

 starch and sugar and tannin, and had made a fairly good 

 growth. 



Red. — Under the red screen the plant approached still 

 closer to the normal. Assimilation went on rapidly, so 

 rapidly in fact, that the cells became gorged with starch. 

 At the end of five or six days so many granules, and such 

 large ones, surrounded the pyrenoids that the bands were 



