MUL TINUCLEA T.E 



287 



which escape into the surrounding water by the removal of the hd. It 



would appear from de Bary and Strasl)urger's observations that some 



of these swarm-spores germinate directly, while others conjugate to form 



a zygosperm ; but that conjugation never takes place between zooga- 



metes from the same spo- 



range. One species of Ace- 



tabularia is a native of the 



Mediterranean ; the rest are 



troijical. In Dasycladus Ag. 



the spherical zoosporanges 



stand singly at the apex of 



verticillate branches, and are 



surrounded bv branchlets of 



the second order. The bicili- 



ated zoospores or zoogametes 



are of one kind only, and are 



flattened and heart-shaped. 



Those from the same plant show no disposition to conjugate ; but as 



soon as those from different plants are brought together, true zygosperms 



are formed. In Xeonieris Lmx. the surface consists of a large number 



of usually hexagonal facets, and is covered with deciduous hairs. The 



Fig. 253. — Dasycladus clavepfor7nis Ag. a. natural size ; 

 b, piece of branch of a svhorl with a zoo5porange ( x 50). 

 (After Hauck and JJerbes and Solier ) 



Fig. 254. — NeojJieris Kelleri Cram. ; transverse section through tube, a, insertion of 

 the branches ; b, b, primarj- branches ; c, central secondary branch or zoosporange ; 

 ^, elongated lateral secondary' branches ( X 40). (After Cramer.) 



very large axial cell is always simple ; the lateral branches again divide 

 into three branchlets, of which the central one is ovoid and fertile, the 

 two lateral ones greatly elongated and sterile. The fertile branch is a 



