430 Mr Gustav Mann's 



is only indirectly in communication with the pyrenoids by 

 means of the first-mentioned threads, that in a species which 

 I found in February 1889 in the pond in the lioyal Botanic 

 Gardens, and the name of which I am unable to determine 

 {vide fig, 7), the chlorophyll-bands touched the nucleus 

 directly. Each cell contains three chlorophyll-bands, and as 

 these approach the nucleus the spirals become steeper, the 

 bands broaden out, and are closely applied to the surface of 

 the nucleus, forming a complete bag, which seems to replace 

 the threads. Eemarkable is also the fact that the bag is 

 packed with pyrenoids, which will act as a storehouse of 

 nourishing material close to the nucleus. As I was not 

 able to find this form of Spirogyra during last summer, it 

 is possible that it may just be an ordinary species, which 

 in this way has become modified to enable it to perform 

 its functions during the cold spring months. 



If Spirogyra material is placed in water to which a few 

 drops of a 10 per cent, gold chloride solution have been 

 added, the gold chloride will be reduced by the action of the 

 threads joining the pyrenoids and the nuclei. I find, at least, 

 the gold chloride deposited as small black granules along 

 the course of the threads; but in addition to this, the gold 

 chloride in the water is also reduced, imparting a beautiful 

 violet colour to the water on transmitted light. 



About ten years ago Dr Macfarlane observed crys- 

 tals in Spirogyra, and according to a notice in Nature 

 (1888), Strassburger has also observed them. My investiga- 

 tions, which were carried on mainly during the winter of 

 1889-90, enabled me, for this very reason, to pay special 

 attention to these crystals, for during the colder months of 

 the year, when the cells are merely vegetating and growing 

 to exceptionally large sizes, the number of crystals in a cell 

 may increase from two or three up to seventeen, this being 

 the largest number of crystals I counted in one cell. The 

 crystals are of common occurrence in S. nitida and S. 

 jugalis growing in Duddingston Loch ; they occur commonly 

 in the form of a cross with slender pointed arms, as repre- 

 sented in fig. 8, h ; by a fusion of a number of these crosses, 

 forms, as represented in d and/ are brought about. The 

 crystals represented in figs, g and h I saw only once in a 

 thread ; the knobs were quite distinct, and had not the 



