164 LINI**AN ARTIFICIAL SYSTEM. 



tuted by plants in which the herbage is sometimes 

 leafy, sometimes a mere crust, and sometimes of a lea- 

 thery or gelatinous texture. The seeds are either 

 embedded in the frond itself, or in some peculiar recep- 

 tacle, and the barren flowers are very imperfectly known. 



The most common distribution of the tribe of algse, is that by which 

 they are divided into the six following genera. 



a. The Lichenes or Lichens^a numerous tribe growing in all 

 climates and in most situations ; the fructifications of which, for 

 the most part, consist of a smooth round disk, flat, convex, or con- 

 cave, with or without an adventitious border, in the substance of 

 which disk, the seeds are lodged. In some others, they are placed 

 in powdery warts or in fibrous receptacles. (F. 196.) 



b. Tremellw Those species of algffi which appear on rotten wood, 

 grass, and in moist weather, in the form of heaps of jelly. Their 

 organization is not yet known. 



c. Fuci Comprehending the different vegetable productions com- 

 monly called sea-meeds ; the seeds of which are collected together in 

 tubercles or swellings, of various forms and sizes. 



d. Ulvae The plants of this division are also aqnatic, and their 

 character well denned by the seeds being dispersed under the cuticle, 

 throughout the membranous or gelatinous substance of the frond. 



e. Conferva; Likewise a division of aquatic alga:, characterized 

 by their capillary and articulated structure, and by the seeds of some 

 species being lodged in external capsules or tubercles, and of others, 

 in the joints of the frond. (F. 195.) 



f. Byssi comprehending such species of algse, as exist in the 

 form of a most delicate downy substance. They are usually found 

 on old wood, in moist situations. 



172. Fungi or mushrooms : This order is composed 

 by a tribe of plants of a fleshy substance, generally of 

 quick growth and short duration, differing in firmness, 

 from a watery pulp to a leathery or even woody texture. 



Belonging to this order we have the following illustrations. Mush- 

 rooms or agarics, are a very extensive genus, grow horizontally, and 

 arc furnished with laminae or gills on the under surface. Thr 



