of Terrestrial Algae. II. 
721 
F. The Nature of the Granules found in the Cells of 
Terrestrial Algae. 
We have been able to obtain evidence which shows that in the cells of 
several of the terrestrial algae examined the granules are of at least two 
kinds. Those of the one kind are minute, relatively uniform in their size 
and distribution, which is frequently peripheral, and are characterized by 
the fact that, whereas they fail to give any of the usual fat reactions, they 
stain a dark colour after a longer or shorter treatment with silver nitrate 
without exposure to light. In the case of Zygogonium half an hour’s treat¬ 
ment with the reagent suffices, whilst in Hormidium and Pleurococcus 
a much longer period is requisite and it has been found necessary to add 
glycerine to the reagent in order to facilitate its penetration. In some cases 
there are relatively few of these granules (especially Pleurococcus). They 
have not been observed in Prasiola. 
The granules of the other kind are larger and irregular in distribution 
and appear to differ somewhat in their reactions in the different forms. In 
Zygogonium they give the normal reactions for fats, both with Sudan III and 
osmic acid ; in Hormidium they stain after some time in the former, but 
appear unaffected by the latter; in Pleilrococcus a certain number of these 
granules stain with osmic acid, but Sudan III has no effect. Possibly, 
however, these differences are only due to differences in the ease of penetra¬ 
tion. In practically all cases the majority of the larger granules are soluble 
in ether, chloroform, and acetone, although in Prasiola solution is only 
attained after a long time (cf. Piercy, 1917 , p. 526). Alcohol dissolves them 
in Zygogonium and to some extent in Prasiola , but apparently not in the 
other cases. The large granules are evidently of the nature of fats and are 
possibly the only kind present in Prasiola. 
Ether and acetone appear quite often to remove all the granules in the 
cells, whilst with chloroform, at least in the case of Zygogonium, the small 
ones remain behind, and, after such treatment, can be brought out clearly by 
subsequent staining with silver nitrate. In the case of Hormidium and 
Pleurococcus we have been unable to arrive at any definite conclusion on 
this point. 
G. General Conclusions. 
The methods adopted in the present investigations are described on 
pp. 683, 689-91, 700, 704, 706, 712, 718, and 720, where also the extent 
of error involved is considered. The most important facts that have been 
established are: 
1. With a given strength of sea-salt solution there is great inequality in 
the behaviour of the cells of the terrestrial algae investigated, as well as of 
3 R 2 
