526 Piercy.—The Structure and Mode of Life of a 
Stichococcus subtilis ; in the Zygnema , however, they commonly occur 
distributed in the whole peripheral layer of the protoplasm. 
The refractive bodies of the Zygnemaceae ( Zygnema and Spirogyrd) 
have been referred to variously as tannin-vesicles 1 and fat-bodies . 2 
According to Klercker , 3 those of Stichococcus subtilis have been constantly 
recorded as ‘ oil but fail to show any distinct fat-reactions. As in the 
case of Stigeoclonium , he succeeded in staining them with Bismarck brown 
and aniline dyes, without killing the cells. 
The frequent occurrence of white refractive granules in the cells of 
many different Algae suggests that there may be some product, common to 
their metatobic processes, which assumes this form under certain conditions. 
Such a view could only be corroborated by a large amount of experimental 
work, but the similarity in the appearance of the different granules and in 
their behaviour towards reagents , 4 as well as their accumulation under like 
conditions , 5 may indicate some such fundamental relationship between them. 
The granules found in the Woodford Hormidium do not appear to be 
of the nature of ordinary fat, since they fail to dissolve in the usual fat- 
solvents (e. g. ether, benzole, carbon bisulphide) and are not saponified by 
treatment with a mixture of concentrated ammonia and caustic potash . 6 
On the other hand, osmic acid stains them brown, though never black, and 
Sharlach R colours them light red, but not deep red as in the case of fats. 
They retain their form after treatment with boiling water. 
Apart from the above, the granules show the following chemical 
properties : They are insoluble in concentrated sulphuric acid ; are unstained 
by iodine ; coloured green by chlorophyll , 7 and reddish-brown by a solution 
of iodine in potassium iodide with subsequent addition of dilute sulphuric 
acid . 8 These reactions, besides those with osmic acid and Sharlach R, are 
all more particularly characteristic of cuticle, and would appear to indicate 
that the granules are composed of some fat-like substance similar to that 
occurring in a cuticularized wall . 9 
In the case of large granules or masses, the interior appears to stain 
more deeply than the peripheral layer when the above reagents are applied. 
This differentiation is marked on staining with methylene blue , 10 the interior 
1 Van Wisselingh : Koninkl. Akad. v. Wetensch., Amsterdam, 1910. 
2 Cf. de Bary, l.c., p. 10; West and Starkey, 1 . c., p. 198, and Zimmermann, Botanical 
Microtechnique English translation by J. E. Humphrey, 1893, p. 234. 3 1 . c., p. 93. 
4 This is not quite the same, however, in all cases. Cf. Fritsch, 1 . c., p. 144. 
8 Cf. Fritsch, l..e., p. 143, and Klercker, 1 . c., p. 94. 
6 Cf. Zimmermann, 1 . c., p. 73. 
7 When cells are heated in water or placed in alcohol, the granules absorb the chlorophyll from 
the chloroplast. The localization of chlorophyll which results is very noticeable, especially as it does 
not occur in non-granular cells present in the same filaments. 
8 As described by Strasburger: Practical Botany, English translation by W. Hillhouse, 
pp. 47 and 395. 9 Cf Zimmermann, 1 . c., p. 152. 
10 Recorded as a stain for fat by Lee : The Microtomist’s Vade Mecum, 1893, 3rd ed., p. 80. 
