ALGM. 



233 



shape with two cilia ; it is endowed with motion like a swarm-spore, but its entrance 

 into the oogonium has not yet been observed. The effect of fertilisation is seen in 

 the oogonium by its contents becoming surrounded with a membrane of its own, forming 

 the oospore. This now grows considerably, and at the same time the formation of the 

 cortical layer (r) of the oogonium commences, while out of the cells that' support it pro- 

 ceed branches (A, og") which cling closely to it. These again form branches which also 

 cling closely and divide transversely ; the branchlets of other branches also ramify (B) ; 

 and only the neck of the oogonium does not become covered with the cortical layer. 

 All this happens between INlay and July ; later, the contents of the remaining cells of 

 the i)lant disappear, and the walls of the cortical layer of the oogonium assume a deep 



Fig. 165.—^/ part of a fertile thallus of Coleochate pi4lvinata (X3S0); B ripe oogonium enclosed in its cortical layer; 

 C germinating oogonium, in the cells of which the swarm-spores are formed ; D swarm-spores (B-D x 280) (after 

 Pringsheini). 



dark-brown colour. The further development of the oospore within the oogonium 

 now covered with its cortical layer begins only in the next spring ; a parenchymatous 

 tissue is formed by successive bipartitions ; the cortical layer splits and is thrown off 

 (Fig. 165, C) ; and from each cell arises an ordinary swarm-spore, and from this again an 

 asexual plant. C. scutata (the most abnormal species) deviates from these processes 

 only so far that in it the oogonia provided with their cortical layer lie on the surface 

 of the disc, and the antheridia are the result of divisions of disc-cells into fours. 



The Floride.^^ are a group of Algae of extraordinarily variable form, belonging, 

 with few exceptions (Batrachospermum, Hildenbrandtia-), to the sea. In the normal 

 condition they are of a red or violet colour ; the green colour of their chlorophyll is con- 

 cealed by a red pigment^, soluble in cold water. They are further distinguished from 



1 Nageli und Cramer, Pflanzenphys. Unters. Zurich, Heft I. 1855; Heft IV. 1S57.— Thuret, 

 Ann. des Sci. Nat. 1855, Recherches sur la fecondation, &c.— Pringsheim, Ueber die Befruchtg. u. 

 Keimung der Algen, Berlin 1855.— [Quart. Joum. Micr. Sc. 1856, vol. IV. pp. 63, 124.]— Nageli, 

 Sitzungsb. der k. bayer. Akad. der Wissen.— Bornet and Thuret, Ann. des Sci. Nat, 5th series, 

 vol. Vil. 1867.— Solms-Laubach, Bot. Zeitg. nos. 21, 22, 1867. 



2 [Also Lemaneacere. Sirodot, Ann. des Sci. Nat. 5th ser. 1872, vol. XVI.— Ed.] 



3 Rosanoff extracted the red colouring matter by cold water, and examined it accurately. In 

 transmitted light it is carmine-red, in reflected reddish-yellow ; the grains of chlorophyll also show 



