FUCACE^E 237 



Dodel-Port (Cystosira) Biolog. Fragmente, pt. i., 1885. 

 Behrens (Fertilisation) Ber. Deutsch. Bot. Gesell., 1886, p. 92. 

 Schiitt (Phycophsein) ibid. , 1887, p. 259. 

 Woodworth (Apical Cell) Ann. of Bot., i., 1888, p. 203. 



Class XIII. Phaeosporeae. 



The Phaeosporese or Phaeozoosporeae form, together with the Fucaceae, 

 the whole of the olive and brown seaweeds of the globe, formerly 

 grouped together under the names Fucoideae, Melanosporeae, or Melano- 

 spermese ; but of many the history of development is at present but 

 imperfectly known ; and when this is ascertained more fully, they may 

 possibly be separated into groups having but little affinity with one 

 another. A number of the Phaeosporeae are epiphytic, and a few 

 parasitic on other seaweeds ; a very few grow in fresh water. 



The ordinary mode of multiplication of the Phaeosporeae is, so far as 

 is known at present, non-sexually by means of zoospores* which occur in 

 all the orders except the most aberrant groups the Dictyotaceae, where 

 they are replaced by motionless spores, and the Syngeneticae. In the 

 Sphacelariaceae there is another mode of non-sexual propagation by 

 means of gemmae or propaguks. Each zoospore has a large red pigment- 

 spot and two cilia, a longer one pointing forwards and a shorter one 

 directed backwards. They differ from those of the green Algse, such as 

 the Confervoideae, in the lateral insertion of the cilia at the base of the 

 colourless apex. They are produced in zoosporanges, which are either 

 external, when they are usually the terminal cells of short branches, or are 

 imbedded in the thallus, in which case they are frequently collected 

 into definite groups or sort, and are interspersed with barren filaments 

 or hyphae, known as paranemes or paraphyses. These are often swollen 

 and club-shaped at their apex ; the zoosporanges sometimes spring as 

 lateral branches from similar filaments. The zoosporanges are of two 

 kinds, unilocular and multilocular (the 'oosporanges' and 'trichospo- 

 ranges' respectively of Thuret). The former are comparatively large, 

 nearly spherical, ovoid, or pear-shaped, and their contents break up directly 

 into a large number of zoospores which escape through a terminal or 

 lateral opening. The latter kind have somewhat the appearance of jointed 

 hairs, and are segmented in the transverse direction only ; or less often 

 are more like the unilocular zoosporanges in form, but are divided 

 internally by both transverse and longitudinal septa. Each cell gives 

 birth to a single zoospore ; and these either escape each separately 



