228 BOTANICAL GAZETTE [SEPTEMBER 
paper.5- He found that the rate of the disappearance of starch from the 
leaves increases with the temperature. When the nights were very warm, 
some plants (Nicotiana, Phaseolus, Juglans, and others) completely emptied 
their leaves of starch in one night. But after cool nights, 6°-9° C., there 
was no perceptible loss of starch in some, and the disappearance was incom- 
plete in others. SaAcus found also that the amount of starch present at any 
time of the day is affected by temperature. At a temperature of 20°-25° C. 
the quantity of starch in the leaves increased steadily from morning until 
evening. But on hot afternoons at a temperature of 30°-35° C. the leaves 
of Helianthus contained less starch than in the morning at 8 o’clock. The 
reason for this phenomenon is found in the fact that translocation from the 
leaf into the stem increases with rising temperature more rapidly than 
photosynthesis. All of these considerations emphasize the important pre- 
caution that to obtain the best starch formation in leaves, the temperature 
should not be permitted to rise above 20°-22° C., which is apparently the 
optimum for this process, as it is for the best general health of such plants 
as are used in these studies. 
Also it must be remembered that plants cannot give good results in this 
or any physiological experiment, when suffering from previous starvation, 
as in the case of pot-bound plants or those which have been kept in darkness 
for a long time; when suffering from over-stimulation from high feeding, 
or from being kept at too high temperatures; and when they have passed 
their grand period of growth. Asa rule plants, and particularly annuals, 
are in their best condition just before flowering —SoPHIA EcKERSON, 
Smith College. 
THE MORPHOLOGY OF RUPPIA MARITIMA—A CRITICISM ¢ 
In section D, “Function of the root,” Graves (p. 113) has wandered be- 
yond the natural limits of his paper as a morphological study, and while the 
propriety of this is perhaps questionable, the basis for this criticism is that 
this section D contains a statement which I think is an unwarranted mis- 
interpretation of some of my own writings, and alse . statement that would 
leave most readers misinformed. I wish first to consider the following: 
“On the other hand, Ponp’s experiments? fail to show conclusively whether 
or not water and dissolved salts are absorbed by the part of the plant above 
5 Arbeit. Bot. Inst. Wiirzburg 3:1 ff., as cited in Ges. Abhandl. 354-387- 
® Graves, A. B., The ane ga) of Ruppia maritima. Trans. Conn- Acad 
Arts & Sciences 14:59-170. 
‘7 Ponp, Raymonp H., 3 biological relation of aquatic plants to the substratum 
U. s. Fish Commission Repod 1903:483-526. 1905. 
