Chlamydomonadese 



173 



starting-point of the various lines of (Jhlorophyceous descent. The history of these is a 

 history of the intercalation of a vegetative phase between two successive motile (Chlamy- 

 domonadine) generations, these motile phases being retained for reproductive purposes as 

 zoospores and gametes ; in the oogamous types the male gamete alone remains motile, and 

 constitutes in the Archegoniate series the last remaining representative of the Chlamydo- 

 monadine cell. 



' The co-existence within the limits of an undoubtedly natural genus of the most 

 primitive form of gamogenesis (the conjugation of equal clothed gametes) with agamogenesis 

 which has the essential characteristics of true oogamy is also a feature of unique interest.' 

 (Blackmail & Tansley, '02.) 



As the genus is of such importance it has received considerable attention from a 

 number of investigators, notably Goroschankin ('90 '91), Dill ('95) and Wille ('03). 



Fig. 102. Colourless members of the Volvocaceaa. A D, Polytoma itvella Ehrenb. ; B, 

 formation of daughter-cells ; C, fusion of motile cells ; D, zygote. E and F, Chlamydoblc- 

 pharis brunnea Franc ; F, division of cell. G, Tetrablepharis ijlobulus (Zach.) Senn. 

 AF, after France, x 660 ; G, after Zacharias (from Wille). 



Two of the most interesting genera of the Chlamydomonadeae are 

 Brachiomonas and Lobomonas, The first-named occurs only in submarine 

 habitats and possesses a cell-body furnished with five horns, all directed back- 

 wards : one straight posterior horn, and four curved horns regularly disposed 

 around the antero-median part of the cell (fig. 101 A F). These horns 

 are hollow outgrowths of the cell, the protoplast extending to their extremities, 

 although the chloroplast generally does not. Lobomonas has only been found 

 in freshwater lakes and pools, and is characterized by the possession of wart- 

 like lobes either at the posterior end of the cell only (L. Francei Dang. ; 

 fig. 101 J) or all round the periphery (L. stellata Chodat ; fig. 101 7). 



Scourfieldia is a recently described genus (G. S. W., '12) which bears 

 exactly the same relationship to Ghlamydomonas that Scherffeliu, does to 

 Carteria. The cells are greatly compressed and contain a cup-shaped 



