53 2 



PART IV. — VEGETABLE TAXONOMY. 



at its base and remains straight at its apex. The twisted portion 

 becomes the archicarp proper, and the straight portion, which is 

 divided by transverse partitions into several cells, serves as a 

 trichogyne to receive the fertilizing influence of the spermatia, 

 after the manner of the Florideae. The archicarp remains buried 

 in the tissues of the thallus until after fertilization, but the tricho- 

 gyne perforates the cortex and comes to the outside. 



After fertilization, which takes place when the thallus is wet, 

 the archicarp becomes invested with hyphae which grow up from 

 below, and the devel- 



'I 





*%, r 



Fig. S35. — Vertical section of apothecium of Anaptychia 

 ciliaris; h, hymenium, producing numerous asci; g, go- 

 nidial layer; r, rind, composed of compact hyphae; m, 

 medulla, composed of loosely arranged hyphae. Magni- 

 fied about 50 diameters. After Sachs. 



oping fruit is carried 

 to the surface, where it 

 forms an organ called 

 the apothecium. This, 

 in all essential respects, 

 is like the fructification 

 of the higher Ascorriy- 

 cetes, having a hymen- 

 ial surface which bears 

 asci and ascospores. In 

 some species the apoth- 

 ecium spreads out its 

 hymenial surface very much as in the fructification of Peziza ; 

 in others, it is closed, and the spores, when ripe, escape from a 

 narrow opening, as in the Pyrenomycetes. Fig. 535 represents 

 a perpendicular section of an apothecium of the former kind. 



Many of the Lichens also multiply asexually by means of 

 soredia. These are gonidia, or groups of them, wrapped about 

 with hyphal filaments, which escape from the Lichen thallus, 

 usually in the form of a fine powder, and germinate immediately 

 to form new plants. 



According to the structure and mode of growth of the thallus, 

 Lichens are ordinarily subdivided into the following groups : 



(A). The Homoiomerous Lichenes. The members of 

 this group have for the most part a more or less gelatinous thal- 

 lus, which is sometimes flattened and lobed, and sometimes fila- 

 mentous, consisting of a gonidial filament with fungus hyphae 

 wrapped about it. Their gonidia all belong to the Cyanophyceae. 



(B). The Crustaceous Lichenes form a numerous group, 



