THE GREEN ALGiE 645 



other forms. There is altogether a marked saprophytic or 

 parasitic tendency in the members of this group. Endosphcera 

 (a space-parasite within dead leaves of Potamogeton) differs 

 appreciably from Chlorochytrium only in its method of repro- 

 duction (see below), but in Phyllobium (occurring in the inter- 

 cellular spaces of the leaves of diverse marsh-plants) we have 

 a form showing a branched siphoneous structure, strongly 

 recalling that of certain Siphoneae (fig. 3, b). A final representa- 

 tive of this group, the genus Rhodochytrium of Lagerheim (45), 

 has completely given up an independent existence, and lives 

 as a colourless parasite in the tissues of Spilanthes Lundii in 

 Ecuador ; the genus owes its name to the blood-red colour of its 

 gametangia, which liberate isogametes, capable also of germi- 

 nation without sexual fusion. The series we have been following 

 up, thus, apart from its siphoneous tendency, also indicates 

 evolution in the direction of parasitism, and it is probable that 

 from some such ancestry a portion at least of the lower 

 Chytridineae may have arisen. The resemblance between 

 Endosphcera and certain species of Synchytrium is certainly 

 astonishing (cf. Lotsy 46, pp. 38 and 1 17). 



All the different members of the Protococcaceae just referred 

 to agree with Chlorococcum in lacking the power of ordinary vege- 

 tative division, but there is a (probably) close ally of this genus, 

 which is characterised by the possession of this faculty. This 

 is Chlorosphcera (Artari 2, p. 35), the species of which occur 

 in freshwater or as space-parasites in water-plants, and have a 

 chloroplast very similar to that of a Chlorococcum, which they 

 closely resemble in outward appearance. Like the latter they 

 also reproduce by subdivision of the contents to form zoospores. 

 At the same time, however, the cells of Chlorosphcera can multiply 

 by ordinary vegetative division, i.e. a division in which the 

 daughter-cells are not provided with a perfectly new membrane 

 (as is the case in Chlorclla), but in which only that part of the 

 membrane is new which serves to separate the two daughter 

 protoplasts from one another. It can hardly be doubted that 

 the development of this method of division was the beginning 

 of the filamentous tendency (also of the flat plate, seen in Ulva, 

 etc.); in Chlorosphcera consociata, Klebs (fig. 3, c), very short 

 threads of cells are sometimes actually formed.* It is, of course, 

 not necessary that the higher filamentous Algae (Ulotrichales) 

 took their origin from a form exactly of the Chlorosph&ra-ty-pe, 



