I 



BOOK II. 



SPECIAL MORPHOLOGY 



AND 



OUTLINES OF CLASSIFICATION 



GROUP I. 

 THALLOPHYTES. 



Under this term are comprised Algce and Fungi (Lichens being also included 

 in the latter section); but the extraordinary variety of their forms and mode of 

 Hfe render it impracticable to characterise Thallophytes collectively by giving 

 prominence to any special features of their growth or reproduction especially 

 alternation of generations, as may be done in the succeeding groups. The 

 most diverse forms of Thallophytes are nevertheless united by a strong and easily 

 recognised bond of natural relationship ; — transitional forms lead, through number- 

 less gradations, from the simplest Algae consisting of round isolated cells, not only 

 to the highly differentiated members of the same class, but also, through the aquatic 

 Fungi and Moulds, to the wonderful forms of the large Hymenomycetes, Gastero- 

 mycetes, and Ascomycetes, the external and internal structure of which deviates 

 greatly from that of all other plants. A detailed account of these relationships 

 would, however, be almost entirely unintelligible to the beginner, since it would 

 presuppose not only a knowledge of the facts now to be explained, but also a 

 more special acquaintance with numerous other forms which cannot be described 

 here. A repeated study of the description of Thallophytes, Characese, Muscinese, 

 and Vascular plants, will exhibit clearly to the beginner the most prominent 

 features of their affinities. One thing only must be mentioned at the outset, — 

 that the term Thallophytes is an adequate one in so far as it points out one 



