DEVELOPMENT OF PLANTS 



235 



hyphae, in fact, a miniature lichen (Fig. 143, C). In some species 

 the soredia form a rather powdery or granular coating on the 

 upper surface of the lichen, and in other cases they are developed 

 within the lichen. These bodies are easily scattered by the 

 wind when the lichens are dry and under favorable conditions 

 grow into new lichens. Reproduction is also effected by means of 

 ascospores that are developed as in the cup fungi. The female 



C 



FIG. 143. 



FIG. 144. 



FIG. 143. Structure of the Lichen: A, section of a lichen, showing the 

 compact arrangement of the hyphae at the top and bottom, also the anchor- 

 ing fungal threads on the underside and the dark algal cells, a, near the top. 

 B, enlarged view of the algae to show their relation to the hyphae. C, dia- 

 gram of one of the powdery particles, soredium, appearing upon certain 

 lichens, showing the hyphae and algae. These bodies are scattered by the 

 wind and form new lichens. 



FIG. 144. Sexual reproduction of the lichen: A, section of an ascocarp, 

 the hymenium appearing as a dark band in the mouth of the cup. B, en- 

 larged view of the asci, a, and paraphyses, p, of the hymenium. 



gametangium is a coiled organ consisting of many cells as in 

 some Pezizales but the male gametes are developed in ascocarp- 

 like bodies where they are formed at the ends of numerous 

 minute hyphae in their origin, therefore, being strikingly sug- 

 gestive of the red algae. In one form, it should be added that a 

 fusion between male and female gametangia has been reported. 



