CARPOSPOREJS. 147 



top or pileus (Fig. 261,^). On the under side of this are 

 the gills, or lamellae (Fig. 261, I), upon whose surface 

 there is developed a continuous spore-bearing layer, or 

 hymenium (Fig. 261, h). The hymeniura consist of par- 

 allel, compacted, elongated, subclavate cells (Fig. 261, K) ; 

 on some of which, namely, the basidia, four (in some spe- 

 cies only two) little pedicels (called sterigmata) arise (Fig. 

 261, si),, and the ends of these enlarge and become con- 

 verted into spores; called, therefore, basidiospores (Fig. 

 261, sp). These soon fall off and germinate, and (so far 

 as is known) give rise to a mycelium. The most numerous 

 and common representatives of this order belong to the 

 genus Agaricus, which has several hundred species. Other 

 common genera are Polyporus, in which the hyraenium 

 lines the walls of vertical pores on the under side of the 

 pileus; Sydnum, in which the hymenium clothes numer- 

 ous dependent spines ; and Stereum, in which the hymenium 

 covers the smooth surface of the sporocorp. Many of the 

 species are edible, and cultivated (as the Mushroom, Agari- 

 eus campestris) for food. It is said that Dr. M. A. Curtis 

 found in North Carolina thirty-eight edible species of 

 Agaricus, eleven of Boletus, nine of Polyporus, seven of 

 Hydnum, and thirteen of Clavaria. Many of the common 

 species are poisonous. 



174. A small group of slender, submerged, aquatic 

 chlorophyll-bearing plants, called Charaeew, should per- 

 haps be mentioned, as additional representatives of the 

 Carposporeae. They have jointed stems, which bear whorls 

 of leaves at regular intervals. The stems in cross-section 

 are one-celled (as in Nitella), or they have a large axial 

 cell, surrounded by many smaller ones, which form a corti- 

 cal envelope (as in Char a). Under the microscope there is 



