FUCACE^ 237 



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

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

 Schiitt — (Phycophaein) ibid., 1887, p. 259. 

 Wood worth — (Apical Cell) Ann. of Bot., i. , 1888, p. 203. 



Class XIII. — Phseosporece. 



The Phceosporeae or Phaeozoosporese form, together with the Fucacese, 

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

 grouped together under the names Fucoide^e, ^Melanosporeae, or Melano- 

 spermese ; but of many the histon,' 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 Phseosporese are epiphytic, and a few 

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



The ordinary mode of multiplication of the Ph^osporese 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 

 Sphacelariace^e there is another mode of non-sexual propagation by 

 means of gemm^ ox propagules. 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 Algae, such as 

 the Confer voideae, 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 sori, and are interspersed ^^ ith barren filaments 

 or hyphse, known as paranemes ox 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, uniloadar and miiltilocidar (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 

 internallv by both transverse and longitudinal septa. Each cell gives 

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



