MARINE ALG^. 



271 



antheridia. In monoecious and dioecious Fuci, the female 

 conceptacles are distinguished from the male ^y their olive 

 colour. The spores are developed in each in the mterior of 

 a perispore, which is borne on a pedicle emanating from the 

 inner wall of the conceptacle. They rupture the perispore 

 at the apex ; at first the spore appears simple, but soon after 

 a series of changes take 

 place, consisting in a 

 splitting of the endo- 

 chrome into six or eight 

 masses, which become 

 spheroidal sporules. A 

 budding-out occurs in a 

 few hours' time, and ulti- 

 mately elongates into a 

 cylindrical tube. The 

 Vaucherice present a dou- 

 ble mode of reproduction, 

 and their fronds consist 

 of branched tubes, much 

 resembling in general 

 character that of the 

 Bryopsidece, from which 

 indeed they differ only in respect of the arrangement of 

 their contents, chlorophyll. In that most remarkable 

 plant Saprolegnia ferox, which is structually so closely 

 allied to Vaucherice, though separated from them by the 

 absence of green colouring matter, we find a correspond- 

 ing analogy in the processes of its development. In the 

 process of the formation of its zoospores, we have an 

 intermediate step between that of the Algse and a class of 

 plants usually placed among Fungi. Cohn has shown us 

 that Piloholus is structually more closely allied to the 

 former class than to that of the latter. Piloholus has 

 a somewhat remarkable ephemeral existence ; the spore 

 germinates about mid-day, the plant grows till evening, 

 re-opens during the night, and in tlie morning the spore-case 

 bursts and the whole disappears, leaving behind scarcely 

 a trace of its former existence. 



Eed Sea-weeds, Floridece, present great varieties of struc- 

 ture, although comparatively little is known of their re- 



Fig. 148. — Development of Ulvce, 



A, isolated cells of spores, b and c, clus- 

 tering of the same, d, cells in the fila- 

 mentous stage. 



