OOSPORES. 



283 



icles. The oospheres are expelled, surrounded by an inner membrane of the oogonium, 

 md escape through the opening of the conceptacle; the antheridia at the same time 

 )ecome detached, and collect in numbers before the mouth of the conceptacle when the 

 fertile branches are lying out of the water in moist air. When they again come into 

 rontact with the sea-water, the antheridia open and allow the antherozoids to escape, 

 the oospheres at the same time escaping from the envelope which still surrounds them, and 



?hich is then seen to consist of two separated layers (Fig. 185, II). The antherozoids 



)llect in numbers around the oospheres, become firmly attached to them, and when 



leir number is sufficiently great, their movement becomes so energetic that they impart 

 the very large oosphere a rotatory motion which lasts for about half an hour. 



''hether the antherozoids force themselves into the oosphere Thuret leaves undecided ; 

 )ut analogy with the processes observed by Pringsheim in Faucheria and (Edogonium 



:arcely admits of a doubt that one or several of them mingle their substance with that 

 )f the naked ball of protoplasm. A short time after these processes are completed, the 



jrtilised oosphere surrounds itself with a cell-wall, fixes itself to some body or other, 

 ind begins, without any period of rest, to germinate, and, lengthening at the same time. 



Fig. i^e^.—Fucus vesiculosus (after Thuret); A a branched hair bearing antheridia; 5 antherozoids ; / an oogonium, 

 C!^ after the contents have divided into eight portions (oospheres), surrounded by simple hairs (/) ; // commencement of 

 the escape of the oosphere ; the membrane {ft) has burst ; the inner membrane i is ready to open (the two together 

 constitute an inner layer of the cell-wall of the oogonium) ; /// oosphere surrounded by antherozoids ; IV, V, germination of 

 the oospore (B x 330, all the rest X 160). 



undergoes first of all a transverse division followed by numerous other divisions. The 

 mass of tissue thus formed puts out from the part on which it rests a root-like hyaline 

 organ of attachment, while the thick free end forms the growing apex (Fig. 185, IV). 



There are numerous marine Algae, included in the group of PhfiBosporesB, which 

 resemble the Fucaceae as well in the structure of their vegetative organs as in the 

 presence of a colouring-matter mingled with their chlorophyll. To this group belong 

 the often enormous Laminarieae (Macrocystis, Laminaria, Lessonia, etc.), as also the 

 smaller Ectocarpeae, Sphacelarieae, Ghordarieae, and Dictyoteae. 



The Phaeosporeae are reproduced non-sexually by zoogonidia, a mode of reproduc- 

 tion which does not occur among the Fucaceae. In some, bodies which appear to be 

 antheridia have been detected, but no oogonia ^ 



^ [Goebel has observed (Bot. Zeitg. 1878) the conjugation of zoogonidia ia two species of 

 Ectocarpus: see also Berthold, in Mittheil. d. Zool. Stat. Neapel, II. 1881.] 



