CHAPTER V.—COMPARATIVE REVIEW.—GASTROMPCETES. 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 carnea 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 Secotieae. 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 collenchyma, the description of which must also be deferred, 
is not yet ‘present; I have never observed its formation. Here too the facts point 
