178 



CnyPTOGAMS 



lar-o bladderlike float filled with air." i The Gulf Weed 

 (^Fig. 2',Jl. C). which collects in such quantities in the so- 

 called Sargasso seas, belongs to this gronp. On certain 

 coasts it grows as an attached plant. Portions which have 

 been detached and carried off by currents continue to grow 

 and multiply vegetatively as they float in the quieter areas 

 of the ocean. 



429. The brownish color of the Brown Algse is due to 

 a pigment in the cells, which probably aids the chlorophyll 

 present in the Avork of assimilation. 



430. Rej.iroduction. — Reproductive cells are of se\'cral 

 sorts in this group. First aud sinqjlest are the zoospores 

 boriic in Zocisporangia (Fig- -02, A), foniid in most 



members of this 



■^Sk^ 



group. Their his- 

 tory is like that 

 of the larger zoo- 

 spores of Ulo- 

 thrix ; that is, 

 they germinate 



* '-* A, 70 )si niuiriiini, aiul B. gainciaiiLiiLiin, of ^-lUeCllV ailCl 



}<ln, up I i_iv: (', sainetfs (r/) and tlieir con- gwarmiug, with- 

 lugatiou (»•). — Pkixgsheim. 



out fusion. 



431. Secondlij. We find processes of cell fusion, not 



unlike those already seen in the reproductive bodies 



of Grpfii Algte. We may select three representative 



cases. ('!) In Ectocarpus and allied plants, zoc'lspores 



(gametes) are produced, which are imlistiiiguisliable frcim 



tlie ziHispor',;s iiitendetl fnr (lire<'t germinati(jn, except that 



the biidies now in mind arisi; in spurangia of a diiTerent 



character (Fig. 292, W). They mav conjugate in pairs (('), 



like the snj:ill zoosj)ores of Ulothrix. (2) In some forms 



(Cutleria), the fusing zoospores (gametes) differ in size. 



The larger come to rest before fusion. This is a step 



intermediate Ijetween the condition in Ectocarpus and that 



next to be described. (3) In the common Rockweed of 



tlie shores, the gametes are c//// eclh and aiifJ.erozouh 



1 Strasburger, "Text Book of Bolanj'," p. 330. 



