524 Reed . — The Value of Certain Nutritive Elements 
In the material studied there was no evidence that the absence of 
phosphorus interfered with the process of starch formation. Cells which 
had died as a result of the absence of phosphorus displayed distinct rings 
of starch in the pyrenoids, and there were numerous starch grains in 
chloroplasts which were so seriously injured that their green pigment 
had disappeared. It seems hardly probable that all of this starch can be 
accounted for by assuming that it is identical with that present when the 
plants were transferred to the phosphorus-free solution. I have previously 
described how the starch originally present in these forms disappeared 
when they were transferred to solutions lacking potassium. It seems 
plausible to believe that a portion of this starch had been formed after the 
plants were put into the phosphorus-free solutions. 
The transformation of starch into water-soluble carbohydrates was 
seriously impaired in cells deprived of phosphorus. In its absence starch 
was transformed into unusual forms of carbohydrate. Some cultures of 
Spirogyra in phosphorus-free solution were kept in diffuse light at rather 
low temperature for four months. This treatment tended to prolong the 
life of the cells by lowering their activity. When, at the expiration of that 
time, the filaments were examined microscopically they showed no signs 
of growth, although most of the cells did not seem to have been seriously 
injured. In nearly all cases there was a considerable quantity of starch 
remaining in the cells. When they were submitted to the action of 
potassium iodide iodine solution for twenty to thirty minutes they showed 
the presence of erythrodextrin. In order to make sure that the reacting 
substance was really erythrodextrin, I placed several filaments of the alga 
in a watch-glass containing a weak solution of diastase. At the end of 
two and one-half hours the tests were inconclusive, but at the expiration of 
eighteen hours there was hardly a trace of erythrodextrin remaining in the 
cells which had lain in the diastase solution. 
The formation of cellulose was increased in a striking manner in the 
same plants in which erythrodextrin was demonstrated. The normal 
thickness of cell-walls in the control cultures of Spirogyra was 5 or 
6 microns, but when grown in the absence of phosphorus many cells 
possessed walls 10 and 12 microns thick. I also observed thickened cell- 
walls in Basidiobolus which was cultivated upon phosphorus-free media. 
It would appear in these cases that it was not possible for starch to be 
fully hydrolyzed, but instead that it was merely transformed into dextrin, 
which probably represents one of the stages in the hydrolysis of starch. 
It was also possible for starch to be changed to cellulose, probably its 
polymeric form. 
The course of the carbohydrates in the cells living in deficient nutrient 
solution indicates quite clearly that the lack of phosphorus interfered with 
the production or action of the enzymes which normally convert starch 
