460 Miss H. Chick. On a Unicellular Green Alga, [Feb. 28, 



This method may be relied upon to yield pure cultures, for it has 

 since been repeated, and again proved successful. 



The following is a fairly comprehensive diagnosis of Chlorella 

 pyrenoidosa. 



CMorella (Beyerinck)* very minute, unicellular, non-motile, spherical 

 or elliptical green algae; chromatophore single, parietal, with or 

 without a pyrenoid; cells isolated, showing no tendency to form 

 colonies ; multiplication by division of the cell-contents to form a 

 number of daughter cells. 



C. pyrenoidosa (sp. n.) : — cells spherical, 3 — 5 /x in diameter, some- 

 times attaining 11 /x ; chromatophore single, parietal mantle-shaped, 

 covering nearly the whole of the cell-wall ; pyrenoid conspicuous and 

 single (see Plate 8, fig 3) ; reproduction by successive division of the 

 cell-contents to form within the mother cell as many as eight daughter 

 cells, which subsequently become free of the mother cell wall (see 

 %• 5)- 



Physiological characters. — Showing a marked preference for ammonia 

 and ammoniacal compounds (e.g., urea) compared with nitrates in its 

 culture fluids ; growth and multiplication largely increased by the 

 addition of glucose to the culture fluids, causing the cells and cell- 

 contents to assume a changed and characteristic appearance. 



Chlorella pyrenoidosa resembles C. protothecoides (Krugerf) very 

 closely, both in its physiology and morphology ; it differs, however, 

 in the possession of a pyrenoid. This pyrenoid with few exceptions 

 is very conspicuous, and can often be stained blue with iodine, being 

 the only part of the cell which shows this staining. C. pyrenoidosa 

 differs also from C. vulgaris (Beyerinck)J in many of its physio- 

 logical properties, as well as by the possession of the well-marked 

 pyrenoid. Its morphology bears, however, a very close resemblance to 

 that of a green alga isolated and studied by Kossowitsch.§ This alga 

 itself resembled C. vulgaris (Beyerinck) and Cystococcus (Nageli)|| very 

 closely, and Kossowitsch decided to call it " Cystococcus," in spite of 

 certain small differences which existed. It has seemed to me the wisest 

 plan to attach the alga, diagnosed above, to the genus Chlorella, and to 

 add a new specific name " pyrenoidosa," although it resembles the 

 Cystococcus figured and described by Nageli, and it seems not unlikely 

 that it may be identical with Kossowitsch's Cystococcus. 



C. pyrenoidosa grows exceedingly well, in pure culture, upon 

 nutrient gelatine, nutrient agar or ammonium agar, and also in many 

 liquid media. In media containing glucose the growth is much 



* ' Bot. Zeit.,' 1890, p. 725 ; ' Cent. f. Bakt.,' vol. 13, 1893, p. 368. 



f Zopf 's ' Beitrage z. Morph. u. Phys. Uied. Org.,' Leipzig, vol. 4, 1894, p. 92. 



X ' Bot. Zeit.,' 1890, p. 725 ; 4 Cent. f. Bakt.,' vol. 13, 1893, p. 368. 



§ ' Bot. Zeit.,' 1894, vol. 6, p. 97. 



|j ' Gattunger einzelliger Algen,' Zurich, 1894, p. 84. 



