HOW TO KNOW THE FRESH-WATER ALGAE 



237b Filaments formed otherwise 



238 



238a Cells orange or golden-red because of haematochrome; plants 

 aerial on trees and rocks; chloroplast dense and indeterminate 

 of shape. Fig. 171 TRENTEPOHL1A 



Fig. 171. Trentepohlia Iolithus (L.) Wall- 

 roth, a, filament with 2 terminal spo- 

 rangia; b, c, sporangia in detail. 



This species and T. aurea Mart, are 

 the 2 which are the most common of 

 the 6 which have been reported from 

 the United States. They grow on moist 

 stones, dripping cliffs, and on the moist 

 bark of trees. The characteristic orange 

 color makes this plant conspicuous, es- 

 pecially when it forms extensive patch- 

 es, sometimes forming a felty-mat over 

 large areas of rocky cliffs. In southern 

 United States the moist sides of trees 

 throughout large areas of the country- 

 side are colored reddish by these algae. 

 In humid situations of the tropics and 

 subtropics the filaments become infested 

 with a fungus to form the lichen, Coeno- 

 gonium. The haematochrome pigment appears in the cell as a re- 

 action to intense illumination. 



Figure 171 



238b Cells without haematochrome; plants aquatic; chloroplast a per- 

 forated and padded sheet or a branched, beaded ribbon. Fig. 

 172 MICROSPORA 



Z^ 



Fig. 172. a, Microspore! Loeigrenii 

 (Nordst.) Lag.; b, M. Willeana Lag.; 

 c, M. floccosa (Vauch.) Thur. 

 In this genus the simple, un- 

 branched filaments have chloroplasts 

 that vary greatly in respect to the 

 degree with which they cover the 

 wall. There are 5 or 6 species, dif- 

 ferentiated by cell size and propor- 

 tions, and by thickness of the wall. 

 Some species show the 2-parted character of the wall, especially at 

 the ends of the filaments where the line of separation having oc- 

 curred in the midregion of the cell rather than at the juncture of 2 

 cells, forms characteristic H-shaped pieces. 



Figure 172 



109 



