230 Chlorophycece 



each cell a parietal plate-like chloroplast devoid of a pyrenoid, 



which is often hidden by an orange- 

 red oil. There are three methods of 

 multiplication ; 1st, by division of the 

 original mother-cell into two or four 

 daughter-cells ; 2nd, by a rejuvene- 

 scence of the cell-contents and an 

 exuviation of the wall of the mother- 

 , *n^T\ p ^ l [ oco f ccusmini - cell; 3rd, by the formation of 8, 



atus (Kutz.) Chodat, from near 



Bradford, w. Yorks. (x720). 16, 32, or 64 spores within the wall 



of the mother-cell, which then rup- 

 tures and sets them free. Palmellococcus differs from Pleurococcus 

 in the absence of pyrenoids from the chloroplasts, in the methods 

 of reproduction, and therefore in the different aspect of the cell- 

 aggregates. 



P. miniatus (Kutz.) Chod. 1 (Pleurococcus miniatus Nag.) is not an in- 

 frequent Alga on the outer surfaces of plant-pots and similar objects, forming 

 a moist, brownish-green scum, which often turns to an orange-red colour. 

 Diam. cells 2 12 -5 /* ; fig. 100. 



Certain plants belonging to this genus have in the past been referred to 

 "Protococcus Ag." The latter genus is obsolete, having included Algae which 

 are now referred to a number of other genera. 



Genus Chlorella Beyerinck, 1890 2 . The cells are small, 

 globular or ellipsoid, with firm cell- walls, and with a single parietal 

 chloroplast containing a pyrenoid. They occur in abundance in 

 symbiotic relationship with Hydra viridis, species of Amoeba, 

 Paramoecium, Ophrydium, etc. Multiplication takes place by 

 the quadripartition of the cell contents. Radais 3 has confirmed 

 Beyerinck's observations that this Alga has the faculty of cell- 

 increase and the formation of chlorophyll in the dark as in the 

 light. Grintzesco 4 also affirms that development takes place more 

 rapidly in total darkness than in full daylight. The latter author 

 has cultivated Chlorella in various media and finds that glucose 

 stimulates its development and that peptone is a better source 

 of nitrogen than nitrates. Cultures of this Alga do not liquefy 

 gelatine. 



Chi. vulgaris Beyr. is widely distributed and often abundant in cultures 

 or in stagnant aquaria. The cells are 5 10 /i in diameter. 



1 Chodat in Bull. Herb. Boissier, torn, ii, 1894, pp. 429 and 599. 



2 Beyerinck in Botan. Zeitung, xlviii, 1890. 



3 Radais in Comptes Rendus, cxxx, 1900, p. 793. 



4 J. Grintzesco in Rev. Gen. Bot. xv, 1903. 



