108 Chlorophycece 



more often they do not. A number of oospheres are developed in 

 each oogonium, and a very large number of antherozoids arise by 

 the breaking up of the red contents of an antheridium. The 

 antherozoids are small, elongated bodies, provided with two long 

 cilia, and they find their way into the oogonia through apertures 

 in the transverse walls. After fertilization, which takes place 

 within the oogonium, the oospores develop a thick verrucose 

 cell-wall and the cell-contents become bright red in colour. The 

 oospores generally hibernate within the oogonium, and this is the 

 most striking condition of the Alga, which now consists of long 

 filaments, most of the segments of which are filled with numerous, 

 bright red, verrucose oospores. 



On the germination of the oospore from two to eight zoospores 

 are set free, representing the sporophyte generation, and each of 

 these forms a new plant. The young plants are simple,, fusiform 

 cells, with each extremity attenuated to a very fine point. 



Bohlin has suggested the transference of this family to the 

 order Siphonese in close proximity to the family Valoniaceae. 



Genus Sphseroplea Ag., 1824. The thallus consists of un- 

 branched filaments of cylindrical coenocytes, which may only be as 

 long as their diameter or up to ninety times longer. The filaments 

 are 36 72 /u, in diameter. 



The only known species Sph. annulina (Roth) Ag. is not a British 

 Alga. It occurs extensively on inundated portions of the plains of Europe, 

 Asia and America, and is sometimes found in pits or quarries. It is question- 

 able if there are any suitable localities for this plant in the British Islands. 

 It sometimes occurs in Kew Gardens, having been introduced from abroad 

 with various aquatic plants. 



Order VII. SIPHONED. 



The order Siphonese embraces a large number of filamentous 

 Algse of many diverse forms. They are cosnocytic in character, 

 the individuals being without septa, so that in reality each plant 

 consists of a single large coenocyte. They are mostly marine Algae 

 and some of them attain a considerable size. The thallus fre- 

 quently becomes very complicated in character, but even then it 

 consists of the interlaced branches of a single multinucleated cell. 

 Nowhere else in the vegetable kingdom do such gigantic cells 

 occur, and it is this extraordinary complication of a single cell 

 which distinguishes the Siphoneae from all other Alga?. Many of 



