116 



BOTANY 





certain Fungi; and this, together with certain structural resem- 

 blances, suggests the derivation of some of the lower Fungi from 

 Algae. 



Order VI. Characeae 



The Characese, or " Stoneworts," as they are sometimes called, on 

 account of the abundant deposit of calcium-carbonate in many of 



them, differ so much from 

 the other Algae as to make 

 their position in the sys- 

 -og tern very doubtful ; and 



they are sometimes re- 

 moved entirely from the 

 Algae. 



The Characeae are, for 

 the most part, fresh-water 

 plants of moderate size, 

 usually a few centimetres 

 in height, sometimes a 

 metre or two in length. 

 They all are much alike in 

 structure, and the order is 

 a very natural one. 



The plants always grow 

 from a single apical cell, 

 and show a regular succes- 

 sion of nodes and inter- 

 nodes, with the lateral 

 members growing in whorls 

 from the nodes. The lat- 

 eral appendages are usually 



FIG. 88. A, Vaucheria sessilis, with oogonium, of two kinds: branches of 

 Oflr, and antheridium, an (X 200). B, V. aversa, limited growth (usually 

 with ripe oospore, sp (x 200). C, zoosporan- called l eaves ) and a smaller 

 gium of V, sessilis. D, active, E, germinating, , ,, , ' , , . , 



zoSspores of v. sessilis. number of branches which 



are, in their structure, en- 

 tirely similar to the main axis from which they spring. The plant 

 is fastened to the ground by numerous colorless roots. 



Cell-structure. The cells of the Characeae may reach a very large 

 size ; the long internodal cells sometimes attain a length of ten cen- 

 timetres or more, with a diameter of nearly a millimetre. In all of 

 the cells exposed to the light there are numerous oval chromato- 

 phores, arranged in rows, usually running obliquely (Fig. 93, C). 

 At one place, marking the boundary between the ascending and 

 descending parts of the rotating protoplasm within the cell, is a 



