12 BOTANICAL GAZETTE [july 



1 8), Pholiota (17), and Hypholoma (i). In all of these forms the 

 differentiation of the pileus takes place in very much the same 

 manner, 



ORIGIN OF HYMENOPHORE AND ANNULAR PRELAMELLAR CHAMBER 



The first trace of the origin of the hymenophore can be seen in 

 the median longitudinal section of the basidiocarp shown in figs. 54 

 and 80, where the under surface of the pileus seems to take the stain 

 more deeply. In this region the filaments are more slender, with 

 dense protoplasmic contents, and lie more or less parallel to each 

 other, thus marking the primordium of the hymenophore. Just 

 below^this there is a spreading of the filaments in the still undifferen- 

 tiated ground tissue lying between the primordia of hymenophore 

 and stipe, due to the rapid growth in the primordial parts. This can 

 also be seen in the tangential longitudinal section of the same fruit 

 body (fig. 55), which was taken midway between the stipe and the 

 margin of the pileus. Figs. 56 and 57 are median and tangential 

 longitudinal sections of an older basidiocarp, the tangential section 

 representing the condition just beyond the stem. Higher magni- 

 fications of the same sections are shown in figs. 81 and 84. Here 

 the differentiation has become much more definite. All parts of the 

 basidiocarp are clearly distinguishable. An annular ring of defi- 

 nitely compacted, downward growing filaments which make up a 

 quite clearly defined, uniform palisade layer is present, and the 

 loosening of the tissues below the palisade layer is much more 

 pronounced. A continuation of this development is seen in the 

 median and tangential longitudinal sections shown in figs. 58 and 59, 

 and more highly magnified in figs. 82 and 85. Here the palisade 

 layer is well developed, and a more or less complete annular rift 

 has occurred below the palisade layer, due to the continued expan- 

 sion of the more actively growing parts. The filaments making 

 up this palisade layer are scarcely i . 5 ju in diameter, and lie closely 

 packed together and parallel to each other. 



ORIGIN AND DEVELOPMENT OF GILLS 



Figs. 60-63 show a fruit body when the first signs of gill develop- 

 ment are distinguishable. Thegills originate as downward growing, 

 radial folds of an even pahsade layer. These folds extend down- 



