114 PLANT LIFE. 



further in the CutleriacecB, and completed in the next order 

 to be considered — the Fucacece, where we find the oosphere 

 a perfectly motionless body from its earliest differentiation. 



In the CutleriacecB, besides the asexual mode of repro- 

 duction by motile zoospores, the only method known to 

 exist in the genus Agalozonia, a true sexual mode of repro- 

 duction occurs in the genera Cutleria and Zanardinia, the 

 female organ being an oosphere, the male a ciliated 

 antherozoid. The oogonia divide into thirty-two or sixty- 

 four cells, each of which produces a single oosphere. The 

 oospheres escape as biciliated active zoospheres, closely 

 resembling the zoospores of the Phceosporece. proper, but are 

 larger. After moving about for some the cilia are retracted 

 and the oospheres become motionless, when they are- 

 approached by the active antherozoids. The coalescence of 

 a single antherozoid with an oosphere is sufficient for 

 effecting fertilization, a cell-wall is then formed, and the 

 oospore germinates at once without entering into a resting- 

 stage. 



Fucacese. 



The FucacecB resemble the Fkceosporea in having the 

 green chlorophyll masked by the presence of the olive- 

 brown colouring-matter called phycophasin, but are charac- 

 terized by the absence of any asexual mode of propagation 

 and by the characteristic mode of sexual reproduction. 



The species included in Fucacem are marine, and con- 

 stitute the bulk of olive-brown seaweeds growing between 

 tide-marks, the common " bladder-wrack," Fucus vesiculosus, 

 being especially abundant on our coasts. The thallus is 

 usually lg.rge, often several feet in length, and usually 

 variously branched, the branches all lying in the same plane ; 



