134 
ON THE PILOBOLIDiE. 
Our attention will now be confined to the Pilobolidae, the 
group which is highest in organisation and which contains 
the most remarkable and interesting species. Several of 
these are so easily obtained and form such pretty objects for 
microscopical display that it is strange they are not more 
frequently used for that purpose. It suffices to put a small 
piece of horse or cow dung beneath a bell-glass or inverted 
tumbler, preferably on a little damped Sphagnum or other 
moss; in a few days it will probably produce a crop of 
Pilobolus and may continue to do so for several weeks 
together. It is true that some students of nature may recoil 
from the unsavoury habitats in which Pilobolus usually, but 
not invariably delights, but as one of the monographers of the 
genus observes “ La science ennoblit tout.” 
§ 2.—The PiLOBOLimE. 
The PilobolidaB are distinguished by the heterogeneous 
membrane of the sporangium, that is to say, by the fact that 
it consists of two portions of very different characters. The 
upper portion (Fig. 8a) becomes thicker and tougher as the 
sporange approaches maturity, and at last almost absolutely 
black. But a narrow zone (Fig. 8b) near the point of junction 
with the stem, distinguished from the rest by its transparency 
and want of colour, is diffluent, that is to say, in the presence 
of water it becomes disintegrated or broken up into a number 
of minute granules, which pass away. This may take place 
without the removal of the upper portion of the sporangium 
from its position. The spores are embedded in a gelatinous 
mass, which retains its globular form even after the 
disappearance of the diffluent zone, and the cuticularised 
hemisphere remains seated upon this like a cap ; its 
edges, however, usually curl up somewhat, and it fre¬ 
quently loses its regular shape, becoming angular and 
puckered (Fig. 5). If sufficient moisture be present, 
the gelatinous mass swells up by imbibition of water, 
and with the contained spores protrudes through the 
open zone in a very characteristic manner (Fig. 5). 
These phenomena, which follow from the disappearance of 
the diffluent zone, constitute the dehiscence of the sporange, 
and are displayed by all the Pilobolidae. This group is 
divided into two genera, Pilobolus* and Pilaira,f which are 
distinguished by the mode in which they effect the dispersion 
of their sporangia, the mode in each case being intimately 
* From 7 riXos, a hat, and /3d\Aw, I throio. 
f From mXos, and a’ipu, I raise. 
