REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



35. At the period of the formation of the 

 spores, the receptacle of Geaster (fimbriatus) 

 is a solid body of a depressed spheroidal form. 

 It presents for examination a central mass and 

 a peridium, the tissue of the latter being con- 

 tinuous with that of the former only at the 

 base. The central mass or kernel is originally 



Fig. H3. 



Diagram of receptacle of Geaster fimbriatus. 



The kernel, a, is surrounded by its reticular mem- 

 brane, which is indicated by the inner of the two 

 double lines. The outer double line corresponds 

 to the resistant external layer of the peridium. 

 The intervening space, 6, is occupied by a delicate 

 tissue of spherical cells. At c, all these struc- 

 tures are continuous, as well with each other as 

 with the mycelium from which the whole ori- 

 ginates. 



solid, but when fully developed, presents 

 numerous irregular cavities, which are scat- 

 tered through its substance. It is entirely 

 composed, when in the solid condition, of 

 delicate filaments similar to those of mycelium, 

 the arrangement of which is as follows : The 

 superficial filaments are closely woven toge- 

 ther, so as to form a delicate reticular mem- 

 brane, which invests the whole kernel, and 

 from the inner aspect of which a second and 

 very numerous, set of filaments passes off 

 towards the centre. It is of these, or of their 

 ramifications, that the corky, semi-elastic sub- 

 stance of the kernel is entirely formed. If we 

 examine the cavities which have been men- 

 tioned as existing in the fully developed con- 

 dition, we find that they are furnished with a 



Section of a portion of the young receptacle of Geaster 



rufescens, about 100 diam. 



The section has passed through one of the cavi- 

 ties, and shows the arrangement of the basidia 

 which form its lining membrane. Some of these 

 bear spores on their summits. 



more or less continuous lining of basidia, bear- 

 ing spores on their summits. These basidia 

 have been shown, by careful observation, to 

 Swpp. 



225 



be in fact the swollen terminations of the 

 centripetal branching filaments above men- 

 tioned. The peridium it is less necessary to 

 describe, as it has no immediate connection 

 with the spore-bearing organs. It consists of 

 an internal and an external layer, the latter 

 being smooth and very resistant, while the 

 former consists of delicate, transitory, spheri- 

 cal cells. In the ripe condition of the Geaster, 

 the peridium becomes detached, at the same 

 time splitting from apex to base in a remark- 

 able and characteristic manner. Geaster may 

 be considered as the type of a well-known 

 family, including the Ly coper dons, Bovistce, 

 and others, all of which are characterised 

 by the presence of a solid receptacle, furnished 

 with numerous spore-bearing lacunae. In al- 

 most all of these Fungi, the arrangement of 

 the spores with their pedicles in relation to 

 the basidia are the same, four pedicles ema- 

 nating from each basidium. In the ripe con- 

 dition the spores are always of a dark-brown 

 colour, frequently approaching to black, and 

 their surfaces are beautifully reticulated with 

 linear furrows, between which there are little 

 conical projections. Each spore possesses an 

 external reticulated, and an internal homo- 

 geneous membrane. This last encloses a 

 cavity, which is occupied by a fluid, which 

 contains numerous oleaginous granules. The 

 ripe spores, after their detachment from the 

 basidia, lie loose in the lacunas of the recep- 

 tacle from which they are set free by the dis- 

 integration of the basidia, as well as of the 

 filament with which they are connected. 

 In this manner, in Geaster, the kernel is con- 

 verted into a bag, formed of the delicate reti- 

 cular membrane, described above as its proper 

 investment. This bag contains a dark-brown 

 diffluent mass, composed of the remains of 

 the basidia and filaments along with ripe 

 spores. Finally, the membrane gives way, and 

 the spores are disseminated in the shape of a 

 light, dry-looking powder. 



36. We next pass to the consideration of 

 the Fungi, among which the spore, instead of 

 being produced at the summit of a basidium, 

 or at the extremity of a simple filament, is 

 formed in the interior of a vesicle or pouch, 

 which is called a theca or ascus. Of these, 

 the first which we shall mention belong to a 

 group of subterranean plants, of which the 

 truffle is the best-known example. The recep- 

 tacle of the truffle consists of a fleshy mass, 

 throughout which numerous sinuous cavities 

 are interspersed. Each cavity is partly lined, 

 partly filled with the thecae and the cells upon 

 which they are supported. This receptacle, 

 like that of all other Fungi with which we are 

 acquainted, originates from a pre-existing 

 mycelium. In its unripe condition it displays 

 on section a number of sinuous empty cavities, 

 which either communicate with each other, 

 or open at one or more points of the external 

 surface. As the truffle advances towards 

 maturity, the cavities are obliterated by the 

 formation of a whitish tissue ; so that on sec- 

 tion, we observe the whole to consist of two 

 substances the one translucent, of firm con- 



Q 



