SECTION 17.] 



TIIAU.OPHYTES. 



169 



a small orifice which in each Bgure is at the margin of the page. The large 

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

 filaments of the antheridia fertilize the large spores after injection Into the 



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

 510. The Floridea or Hose-red scries of marine Algae (which, however, 



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



The delicate Porphyra orLaver is in some countries eaten as a delicacy, and 



the cartilaginous Cuondrua crispus has 

 been largely used for jelly. Besides their 

 conceptacles, which contain true spores 

 (Fig. 500), they mostly have a fructifi- 

 cation in Tetraspores, that is, of spores 

 originating in lours (Fig. 559). 



500 



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

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



ISA 



■Mi 



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



Fig. 567. Small plant <>f Chondrus crispus, or Carrageen Moss, reduced in 

 si/c in fruit; the spots represent the fructification, consisting of numerous tetra- 

 iporea in bunches in the substance <>f the plant. 558. Section through the thickness 

 of one of the lobes, magnified, passing through two of tlio imbedded fruit-clusters, 

 559. Two of its tetraspores (spores in fours), highly magnified. 



Fig, 560. Section through a conceptacle of Delesaeria Leprieurei, much magni* 

 Bed, showing the spores, which are single specialised cells, two or three in s row. 



fro. 561. a piece of the rose-red Delesseria Lepreiurei, double natural site. 

 i">o-j. a piece cut out and much magnified, showing that it is composed of a layer 

 »f cells. 568. a f.-w of the cells more highly magnified: the cells arc gelatinous 

 mnl thick-walled. 



