SECT. ii. OF ALGJR. 181 



ginous or membranaceous Sphserococcoidese. The plants 

 of this group are dioecious, with two kinds of fruit, 

 spores. and tetraspores, and they bear anther idia filled 

 with active spennatozoids. 



The Melanospermese divide into two series, the arti- 

 culate and inarticulate. The former comprise the Ecto- 

 carpese, which are filiform plants with external cysts, 

 and the Chordarise, which are interlaced cylindrical 

 plants with immersed cysts. The latter include the 

 Laminarise, flat, often strap-shaped, sometimes gigan- 

 tic plants, having the spores superficial and indefinite, 

 and the Fucacese, which constitute a large proportion 

 of the shore-weeds of our seas and estuaries, and which 

 bear their spores in elliptic or spherical conceptacles sunk 

 in the frond. The Melanospermese are either monoecious 

 or dioecious, and spermatozoids are general amongst 

 them, though occasionally propagation is effected by 

 means of zoospores resembling the spermatozoids. 



Having thus indicated the several groups of the 

 great Algal family, their structure and development will 

 now be traced, commencing with the most simple forms, 

 which occur among the CHLOBOSPEBME^E. 



Spring water absorbs oxygen, nitrogen, and a large 

 proportion of carbonic acid gas from the earth and the 

 atmosphere, without losing its limpidity, but notwith- 

 standing this apparent purity, if exposed for a time to 

 the sun, green slime appears, and this the microscope 

 shows to be full of globules or vesicles filled with green 

 matter the primordial cell in its earliest form. No green 

 slime is formed in spring water if kept in darkness, so 

 solar light is the principal agent in this growth, which 

 is by no means a spontaneous birth; it is merely the 

 development of one or more of the many kinds of germs, 

 invisible to the naked eye, that exist in the earth, air, 

 and water in myriads, waiting till favourable circum- 

 stances enable them to germinate. 



