378 BOTANY. 



lantic and Pacific coasts. Cera/mium rvbrum is a very common spe 

 cies. 



(c) The order Corallinese was represented in the Silurian by a spe- 

 cies of Oorallip.a. Others occur in the Secondary (Jurassic) and Ter- 

 tiary. Chondrites represented the order Gigartineae from the Permian 

 to the Tertiary (Miocene). The order SphserococcoideEe was represented 

 in the Secondary by Jurassic species of SpK(xruco(xiUs, and in the Ter- 

 tiary by Delesseria. In the order Rhodomeleae a species of Polysi- 

 phonides occurs as a fossil in the Tertiary. 



§ III. Class Ascomycetes. 



370. — This large class includes chlorophyll-less plants 

 which difEer much in size and appearance, but which agree 

 with one another, and difEer from all other Carposporese in 

 producing their spores {ascospores) in sacs (asci). The sex- 

 ual reproductive organs, consisting of carpogonia and anthe- 

 ridia, are produced upon the mycelium, and, after fertiliza- 

 tion, a sporocarp, which includes the asci and ascospores, is 

 developed. The asci are, at first, single cells at the ends of 

 branches which result from fertilization of the carpogonium ; 

 in these, ascospores arise by internal cell-formation. The 

 most common number of ascospores is eight in each ascus, 

 but it sometimes exceeds, and frequently falls short, of this 

 number, there being often no more than one or two. The 

 asci are in many cases arranged side by side in a compact 

 mass, forming a spore-bearing surface, the liymeniuni. In 

 addition to the ascospores there are generally one or several 

 other kinds of spores, which are developed on the same my- 

 celium as the sexual organs, or on another, the latter case 

 being one of an alternation of generations. 



371. — The Ascomycetes are readily separated into a num- 

 ber of well-marked groups, which may not all turn out to be 

 coordinates. For the present they may be treated as orders. 



372.— Order Perisporiaeese (or Erysiphaeese). In this 

 order the plants, which are mainly parasitic, are composed 

 of branching articulated filaments, which form a white web- 

 like film upon the surface of the leaves and stems of their 

 hosts. There are both sexual and asexual spores, and of 

 the latter there are in most cases two or three different kinds, 

 which are produced earlier than those that result from a fer- 



