CHAPTER V. — COMPARATIVE REVIEW. — GASTROMYCETES. 313 



surface of the ground, while the attempts which have been made to cultivate them have 

 not been hitherto successful, and many of the most remarkable species grow in 

 countries which are very inaccessible to botanists. 



However it has been ascertained that as a general rule every compound 

 sporophore consists at first of a close uniform weft of primordial hyphae, in which 

 the changes which produce its definitive condition are effected by internal differenti- 

 ation and new intercalary formations. The case may possibly be to some extent at 

 least different in Gautieria. 



The differentiation begins chiefly with the separation of the gleba and the young 

 peridium and varies, as might be expected, in its further details according to the species 

 or genus and group. The most important of these details will be given in the 

 succeeding paragraphs together with the most remarkable peculiarities that have been 

 observed in the structure of the mature compound sporophores, and some additional 

 and critical remarks will be appended. 



1. Hymenogastreae. Hymenogaster Klotzschii appears not unfrequently along 

 with Octaviania earnea during the winter months on heath-mould in flower-pots in 

 conservatories, growing at first beneath the surface, but soon coming above it. Its 

 compound sporophore, in the earliest stages observed by Hoffmann and myself, is a 

 small spherical body attached by one side to the substratum and the mycelium, and 

 consisting of closely interwoven hyphae with narrow interstices which in part contain 

 air. In quite small specimens 1 mm. in diameter, a median vertical longitudinal 

 section shows a fibrillation radiating from the point of attachment, in older ones there 

 is no apparent arrangement in the weft. The surface has from the first the same close 

 felt of hairs as the mature peridium. Still older individuals show the chambers in 

 the interior of the gleba in the form of narrow, air-conducting, and very sinuous cavities ; 

 that part of the walls which adjoins the cavities contains no air and shows the structure 

 of the hymenial layer. The chambers themselves are filled at first with loosely woven 

 filaments which run from one wall to the wall opposite and gradually disappear. 



These data prove that the parts are formed by the splitting and differentiation of 

 the originally uniform mass of tissue. The formation begins, as far as I could deter- 

 mine, in the periphery and advances in the direction of the base, where a portion 

 of the original tissue (the basal portion) remains unaltered. As the development 

 proceeds the folds in the walls of the chambers become more and more smoothed 

 out and the chambers are thus enlarged. The expansion of the cells of the trama 

 has no doubt much to do with this change. What is known of other Hymenogastreae 

 agrees essentially with the above account. There is nothing of general importance 

 to be added to the remarks which have been made in a previous page on the structure 

 of the mature plant, and the same may be said of the forms included in the group 

 of the Seeotieae. As regards other forms which have been placed by authors with 

 Secotium, especially Berkeley's remarkable Polyplocium, it must be left to further 

 investigations to determine whether they belong to this or to some other place. 



2. Scleroderma and Lycoperdaceae. Specimens of Geaster hygrometricus of 

 the size of a pea consist of a uniform soft tissue containing air and formed of delicate 

 segmented hyphae ; it is of a whitish colour in the inside and brown at the cir- 

 cumference, and is attached to a felted mycelium which often spreads in the soil 

 for the distance of an inch all round. Older specimens, which may be of the size 

 of a hazel-nut in strongly developed plants, show the fibrillose layer of the peridium 

 to be described below, in their periphery; in the interior the hyphae part from 

 one another to form the chambers of the gleba, into which the hymenial hyphae 

 shoot out ; the layer of collcnchyma, the description of which must also be deferred, 

 is not yet present ; I have never observed its formation. Here too the facts point 



