328 DIVISION II. — COURSE OF DEVELOPMENT OF FUNGI. 



The mature peridium of Sphaerobolus stellatus is white and about as large as a 

 grain of mustard-seed, and is found either on the surface of the substratum, which 

 is usually decaying wood, or sunk in it. Its differentiation may be compared with 

 that of Geaster. A thick outer wall encloses a spherical peridium internum about 

 1 mm. in diameter, which in this genus is also termed a sporangium, and at maturity 

 consists to a great extent, and even in its outer surface, of a tenacious mucilage, 

 in which numerous basidiospores and other cells accompanying them are imbedded, 

 When young it contains a gleba formed of delicate hyphae surrounded by a thin hyphal 

 weft next the outer peridium, and imperfectly and irregularly divided into chambers 

 by narrow tramal lamellae containing air. The chambers are Idled with hyphal 

 branches closely woven together and bearing basidia, which usually produce from 

 li\e to seven spores each. Ultimately the hyphae in the compound sporophore are 

 to a great extent disorganised and form the tenacious sticky mucilage mentioned above, 

 which has been carefully studied by E. Fischer. The ripe spores are retained in 

 the mucilage, and with them, especially in the periphery, isolated one-celled or few- 

 celled pieces of the trama or the basidia-bearing hyphae. Some of these pieces become 

 vesicular mucilage-cells several times larger than the basidiospores, and are incapable 

 ot further development, but in their turn suffer disorganisation; others become spores 

 or gemmae of a different kind, which are originally short cylindrical thin-walled 

 cells rich in protoplasm occurring singly or a few together in a row, different in 

 shape from the basidiospores and germinating very readily. They will be noticed 

 again on page 330. The outer wall is composed of two chief concentric layers ; a 

 peripheral, white and floccose on the outer surface, which is again divided into two layers, 

 and an inner layer. The latter separates again into two layers, a peripheral dense fibril- 

 lose layer next within the outer layer, and a collenchyma-layer united to the fibrillose 

 layer, and consisting chiefly of relatively large cells placed radially to the whole sphere in 

 the manner of a palisade. The whole of the outer wall when fully mature bursts at the 

 apex into 6-7 lobes in a stellate manner, and the inner peridium which is filled with 

 spores is not at first moved from its place. The rupture is caused by the greater 

 superficial extension of the collenchyma layer. Growth continues in this layer in 

 the direction of the surface after the rupture of the peridium, and as the other layers 

 do not grow with it, it is in a state of positive tension. Ultimately it breaks loose 

 with the fibrillose layer which adheres firmly to it from the peripheral layer, continuing 

 united to the latter only at the tips of the lobes, and carries the inner peridium on 

 its centre, which is arched strongly outwards. If these processes are made to go 

 on slowly, the peridium remains attached though slightly to the collenchyma-layer, 

 as in Geaster fornicatus. Usually and normally the positive tension reaches a high 

 degree before the separation, which occurs suddenly in consequence of fluctuation 

 in the turgescence, the collenchyma-layer becomes convex outwards with a jerk 

 and a crackling sound, and the inner peridium which is only loosely attached is flung 

 away, in favourable cases to a distance of more than a millimetre, and adheres to any 

 object on which it alights. 



The development of the structural conditions which are at the bottom of these 

 processes, the details of whi< b are to be found in Pitra and E. Fischer, is the result of 

 the differentiation of a coil of hyphae 0] iginating in the branching of the mycelium and 

 at first perfectly uniform. 



Course of development and affinities of the Basidiomycetes. 



Section XCI. The whole courso of the development of a Basidiomyceto 

 was first followed by Woronin in 1867, when he examined the genus Exobasidium. 

 a parasite on living species of Vaccinium. This very simple form consists in the 

 mature stale of a basidial layer, which comes to the surface of the epidermis of the 



