SECTION 17.] 



TlIALLOPllYTES. 



1G9 



a small orifice whicli in each figure is at the margin of the page. The large 

 spores are formed eight together in a mother-cell. The miuute motile 

 filaments of the authericlia fertilize the large spores after injection into the 

 water: and then tiie latter promptly acquire a cell- wall and germinate. 



510. The Floridese or Rose-red series of marine Alga; (which, however, 

 are sometimes green or brownish) are the most attractive to amateurs. 

 The delicate Porpliyra or Laver is in some countries eaten as a delicacy, and 

 tiie cartilaginous Chondrus crispus has 

 been largely used for jelly. Besides theii 

 conceptacles, which contain true spores 

 (Fig. 560), they mostly have a fruetili- 

 cation in T traspores, that is, of sj)ores 

 originating in fours (Fig. 559). 



557 559 



511. The Grass-green Algse sometimes form broad membranous fronds, 

 such as those of the common Ulva of the sea-shore, but most of them form 



m 



pm-^ 



mere threads, either simple or branched. To this division belong almost 



Fig. 557. Small plant of Chondrus crispus, or Carrageen Moss, reduced iu 

 size, in fruit; the spots represent tlie fructification, consisting of numerous tetra- 

 spores in hunclies in tlie .substance of the plant. 558. Section tliroujrh the thickness 

 of one of the lobes, magnified, passing through two of tlie inibedded fruit-clusters. 

 559. Two of its tetrasjwres (sjiores in fours), highly magnilied. 



Fig. 560. Section through a coiiceptacle of Delesseria Leprieurei, much magni- 

 fled, .showing the spores, which are single specialized cells, two or three in a row. 



Fig. 561. A piece of the rose-red Delesseria Lepreiurei, double natural .size. 

 562. A piece cut out and much magnified, showing that it is composed of a layer 

 of cells. r)63. A few of the colls more highly magnified: the cells are gelatinous 

 and thick-walled. 



