PRINCIPAL GROUPS OF PLANTS. 31 



of nearly a thousand feet. Other forms have large floats at the 

 base of the lamina. Reproduction is chiefly by zoospores formed 

 in I -celled sporangia which occur either in dispersed patches 

 or in continuous bands near the centre of the frond. 



Sargassum, or Gulf Weed, grows attached to rocks by means 

 of disk-like hold-fasts (Fig. 14, C). When it is torn from the rocks 

 it is carried into the open ocean by currents such as the Gulf 

 Stream. Sargassum is most highly organized and is represented 

 by a very large number of species. They are found especially in 

 the warmer waters near Australia, Japan and the adjacent coast of 

 Asia, and also in the West Indies and at various parts of the 

 Atlantic Coast near the Gulf Stream, some occurring as far north 

 as Cape Cod. The plants vary from 15 cm. to nearly 2 metres in 

 length, and consist of a stem-like axis which bears leaf-like 

 branches with a distinct midrib, berry-like air sacs on stalk's, and 

 reproductive branches or receptacles. 



Rhodophyce.^. — This includes all the Algae which are of a 

 reddish or violet color. They contain chromatophores in which 

 the chlorophyll is masked by other pigments, mostly red, and 

 known as phycoerythrin or rhodophyll. The red Algse are mostly 

 found in salt water, occasionally in fresh and running water. 

 They are usually found growing upon other plants or variously 

 attached to some substratum. They vary from microscopic forms 

 or very delicate filamentous types to large plants. They are 

 usually composed of a number of cells or filaments which are 

 so closely arranged as to resemble the tissues of higher plants. 

 Many of the cells are connected by strands of protoplasm, giving 

 them a rather characteristic appearance. Others have an in- 

 crustation of lime on the wall. They are mostly found in deep 

 waters of the Tropics. Reproduction is almost entirely by sexual 

 or asexual spores. 



Chondrus, or Carragheen or Irish Moss (Figs. 15, 16), is a 

 common rock-weed found at low-water mark, and in this country 

 is common from New York northward, being extensively col- 

 lected at a few points about 15 to 20 miles south of Boston. The 

 plant varies considerably in color, being more or less green when 

 close to the surface of the water and of a deep purplish-red when 

 growing at some depth. It varies from 4 to 15 cm. in length, and 



