54 DIVISION I. — GENERAL MORPHOLOGY. 



like the spokes of a wheel. They arc closely interwoven at the centre, but separated 

 towards the circumference by constantly increasing interspaces, and thus the surface 

 is covered with spreading hairs. These appear under the microscope to be colourless 

 or of a uniform brownish colour, while the hyphae of the central tissue is coloured by 

 granules of a reddish-yellow pigment. As the development proceeds the lower half 

 of the hemispherical body, lower that is in relation to the substratum which is 

 supposed to be vertical, takes a reddish-yellow tint and its surface becomes smooth 

 and velvety. Thin radial sections following the direction of the hyphae show that, 

 as far as the last-mentioned character extends, numerous hyphae, most of which 

 contain reddish-yellow pigment-granules, have grown from the central weft to 

 the surface and have thrust themselves in large numbers everywhere between 

 the previously formed hairs and enclosed them. The upper half of the hemispherical 

 compound sporophore retains its original character. Now begins a vigorous longi- 

 tudinal and apical growth of the hyphae which run into the margin of the reddish- 

 yellow under surface of the young pileus, while those which terminate in its middle 

 portions elongate but little or not at all. Hence the upper surface becomes concave 

 and the horizontal portion of the pileus raises itself from the substratum, 

 while the growth of the hyphae advances at its margin. Sections show that 

 the margin consists of a massive and compact layer of truncated rather thick 

 hyphal extremities, which incline slightly towards the under surface and usually contain 

 reddish-yellow pigment-granules. These extremities join on to the perfect hyphae of the 

 pileus close to the point of origin of the latter ; these perfect hyphae being distinguished 

 from them by their pellucid contents, but not by greater thickness, and running in 

 radiating lines parallel to the surface of the pileus. The differentiation of the tissue 

 of the pileus begins close behind the advancing margin, and results in a lower colourless 

 medullary stratum, and an upper thin rind-stratum distinguished by membranes 

 of a clear brown colour. Numerous hairs begin to be developed on the upper surface 

 nearer the margin, and the hymenium on the lower surface. The former are simple 

 stout hyphal branches which either spread or are curved backwards ; the outermost 

 of them project beyond and mostly cover the growing margin. Numerous branches 

 run obliquely and with a slight curve close behind the margin towards the hymenial 

 surface. The nearer the base of the pileus, the more numerous are the hymenial 

 elements which are introduced between those previously formed, and the more 

 . decidedly do they assume the vertical position as regards the surface of the original 

 constituents of the hymenium. The portion of the pileus which is attached to the 

 substratum shows essentially the same mode of growth as that which projects from 

 it, only the hairs on its outer surface penetrate as rhizoids into the substratum. 

 Measurements by J. Schmitz and microscopic examination show that the enlargement 

 of the pileus takes place only next the margin 1 . 



4. The unveiled umbrella-shaped pileus with central stalk of the Agarici (Fig. 24) 

 appears at first on the mycelium as a small cylindrical, ovoid, or even spherical body, 

 pointed at the upper end and consisting throughout of very delicate firmly united 

 hyphae running longitudinally. At a very early stage, when the entire structure 

 in the specimens which I have examined is $-2 mm. in length, the extremities of 

 the hyphae at the upper end spread in every direction as they grow and at the same 

 time branch copiously. Thi rise to a small hemispherical head separated 



from the lower portion by a shallow annular furrow, the primordium of the pileus 

 (Tig. 24 a). A vigorous growth then commences in the extremities of the hyphae 

 which form its margin, and they constantly elongate, but at the same time retain 

 their original thickness, and continue as closely woven together as at first ; there 

 must therefore be a constant introduction of new branches between the earlier 

 ones in the direction of the surface of the pileus. The hyphae which run towards 



also R. Hartig, Zersetzungserscheinungen d. Holzes, p. 130, t. W III. 



