254 ALGA£ 



regards this species as probably a non-sexual generation in the cycle of 

 development of Cutleria multifida. The chief argument for placing the 

 Cutleriaceae among the Phasosporese is the occurrence of non-sexual 

 zoospores, but the mode of sexual reproduction indicates a distinct 

 approach to the Fucaceae ; in this latter class, however, the structure of 

 the antherids is quite different. 



Literature. 



Janczewski — Mem. Soc. Sc. Xat. Cherbourg, 1872, p. 345, and Ann. Sc. Nat. ,xvi., 



1883, p. 210. 

 Reinke — Monber. Berlin. Akad. Wiss. , 1876, p. 565 ; and Nova Acta Acad. Leop.- 



Carol., 1878, p. 67. 

 Palkenberg — Mittheil. Zool. Stat. Neapel, i., 1879, p. 420. 



The order DicxvoTACEiE, comprising, according to Bornet, the eight 

 genera Dictyota (Lmx.), Zonaria (Harv.), Stoechospermum (Ktz.), Lobo- 

 spira (Thur.), Spatoglossum (Ktz.), Padina (Adans.), Taonia (Ag.), and 

 Dictyopteris (Lmx.), has been united by some writers with the Cutleriaceae, 

 while by others it has, with much more reason, been erected into a 

 distinct class, of equal rank with the Phseosporeas. It differs, in fact, 

 from the other orders of Ph^ospore^ in several important points. The 

 thallus of the Dictyotaceae is membranaceous, usually erect flat and 

 leaf-like, seldom ribbed, often beautifully variegated in zones from the 

 presence of prismatic hairs or from incrustation of calcium carbonate. 

 Growth takes place either by means of a single apical cell (Dictyota), or 

 from a group of equivalent cells. Non-sexual organs of propagation are 

 known, and other organs which are probably sexual. The Dictyotaceae 

 differ, in the first place, from all other Phaeosporeae in the absence of 

 motile ciliated zoospores. The non-sexual tetraspores are produced in 

 tetrasporatiges developed on the margin of the thallus, or in sori on its 

 surface, on special non-sexual individuals. Although the contents of 

 each sporange usually break up into four spores, when they resemble in 

 all respects the tetraspores of the Florideae, this is not always the case ; 

 occasionally they divide into only two spores, and still less often the 

 entire contents of the sporange escape as a single naked spore. The 

 spores germinate directly, after investing themselves with a cellulose 

 membrane. The presumed sexual organs, oogofies and antherids^ are 

 collected into sori in similar situations, but not on the same individuals 

 as the tetrasporanges. Some species are monoecious, others dioecious. 

 The contents of each oogone consist of a single undivided motionless 

 oosphere. The contents of the antherids, on the other hand, divide into 

 a large number of motionless polUnoids. Up to the present time, however, 

 actual impregnation of the oospheres by the pollinoids has not been 



