MYXOPHYCOPHYTA 



285 



with the colonial envelope. There 

 is every transition from compact 

 (M. aeruginosa) to extremely loose 

 colonies {M. ichthyolabe), the 

 number of cells enclosed in one 

 envelope depending on the rate of 

 division, which only takes place in 

 two planes. In M. elegans, prior 

 to cell division, an accumulation 

 of chromatin occurs in the centre 

 of the cells to form a central body 

 or so-called ^nucleus', which 

 divides by constriction immedi- 

 ately preceding cell division. The Fig. 163 Merismopedia elegans. A, 

 *rmrlpn<;' then Hkannear*; until the portion of colony ( x 345). B, portion 



nucleus tnen aisappears untn tne ^^ ^^^^^^ ^ ^ ^^^^^ ^^ structure in 



next division. The majority of cells about to divide ( x 1875). (A, 



the species are free floating in fresh ^^^^' ^"^'^"^ ' ^' ^' ^^^^' ^^°") 

 waters. 



Chamaesiphonales 



This order, which is a very small one, consists of attached uni- 

 cells which occur either singly or aggregated together into groups. 

 They differ from the preceding group in that reproduction is by 

 means of endospores (gonidia). 



Chamaesiphonaceae: Entopky salts {ento, within; phy salts, httle 

 bladder). Fig. 164 

 The cells of the sole genus in the family are epiphytic, solitary or 

 arranged in dense clusters on other fresh water or marine plants. 

 The cells are more or less rigid, vary much in shape and are attached 

 at the base by down-growing filaments. 

 In a cushion cell division is usually hori- 

 zontal, but the upper daughter cells 

 can divide by perpendicular walls, 

 the resulting arrangement of cells 

 being radial. The sheath is thin and 

 hyaline and ultimately opens at the ^^ l',\fZ^sf;< 330)' 

 apex. Reproduction is by means of (After Geitler.) 





