DEVELOPMENT OF PLANTS 



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sists of a mass of nearly parallel hyphae that show little modifi- 

 cation save at the surface of the stem, where they are sometimes 

 more compactly arranged (Fig. 168, A, B). By cutting across 

 the gills, so that we can look into the ends of them, it will be 

 seen that the hyphae extend down the center of the gills and also 

 continually radiate out on either side, forming a compact layer 

 of rather elongated cells on the surface of the gills, known as the 

 hymenium (Fig. 168, C). A magnified view of a portion of this 

 hymenium shows that it is composed of paraphyses and basidia 

 (Fig. 168, D). The basidia are not divided as in the smuts and 



Fig. 168. Structure of a mushroom : A and B, cross and longitudinal 

 sections of a portion of the stipe, showing the character and arrangement 

 of the hyphae that make up the mushroom. C, tangential view of the 

 gills — p, pileus; h. hymenium appearing as a dark band on the surface of 

 the gills. D, a portion of the hymenium enlarged — b, basidia; pa, para- 

 physes ; s, basidiospores. 



