Germination of Helianthus annuus. 721 
maximum at Stage III, when the cotyledons have just spread out, and from 
that time on it gradually decreases. 
The actual amount of cellulose in the cotyledons changes but little 
during the different stages of the seedlings examined, and the slight varia- 
Lengfh of Time in Days. 
Fig, 21. Reducing Sugar, per cent, of dry material. 
tions noticed are within the limit of error of such a determination. The 
fact that the amount of cellulose does not increase in the cotyledons is 
to be expected, since, as Sachs first pointed out, there is no formation of 
new cells in these parts, but only a stretching of the cells already present. 
A small amount of starch appears in the starch sheath of the hypocotyls 
and roots and in the parenchyma cells of the vascular bundles of the 
to 
Length of Time in Days. 
Fig. 22. Reducing Sugar, grams per ioo seedlings. 
cotyledons during the progress of germination. The quantity is so small, 
however, that the ordinary test with iodine upon the ground-up material 
fails to show any results. Under the microscope, however, the grains are 
plainly visible when sections are cut and stained with iodine. This fact is 
worthy of note, since it serves to show the danger of judging the chemical 
changes which take place in plants by micro-chemical means, unless they 
are substantiated by analytical determinations. The amount of starch 
present here is very small compared to the other carbohydrates, yet by 
micro-chemical methods it is made very conspicuous, and the amount is 
liable to be over-estimated. 
Initial Losses .—Judged on the basis of consumption of material the 
greatest intensity of respiration in the seedling seems to be from the time of 
