440 SECOND PART.—MYCETOZOA. --: 
(peridium), the outer side of which is irregularly warted, while numerous tangled 
threads, a capillitium, stretch from its inner surface into the cavity of the body which 
is filled with spores. The rind is composed of two portions having a layer of finely 
granular mucilage between them and separating readily from each other. ‘The 
inner portion in the surface-view is perfectly homogeneous or finely punctated; seen 
in section it is an evidently stratified membrane about 8 a in thickness and of a 
bright brown colour. The outer and much thicker portion on the other hand is formed 
chiefly of a weft of cylindrical tubular branched threads disposed in several irregular 
layers; the thickness of the threads is usually 20-33 a, and their walls are stratified 
and thick, sometimes 10 a in thickness, the outer lamellae consisting of a homogeneous 
jelly while the innermost layer is of firmer consistence and provided with slit-like pits 
or reticulate thickenings. Numerous branches of these rind-threads bend inwards, 
and piercing through the inner rind appear as threads of the capillitium in-the central 
cavity. Here they have only the innermost lamellae of their membrane which is 
pitted or thickened in a reticulate or sometimes annular manner, the outer lamellae 
coming to an end in the inner rind. The thickenings project outwardly in the form 
of ridges which have the appearance of wrinkles and vary in height and breadth, 
being often very flat. The threads of the capillitium, which are often compressed 
and riband-like, branch and anastomose copiously. Finally the warts on the outer 
surface of the rind are thick-walled closed vesicles filled with a densely granular 
substance. These vesicles are undoubtedly remains of plasmodia filled with excreted 
substances, the whole body having been composed when young of their dense and 
uniform reticulum. The threads of the outer rind appear to be the thickened and 
subsequently emptied membranes of other peripheral plasmodial strands ; the develop- 
ment of the inner part is imperfectly known. 
The space not occupied by the capillitium is entirely filled with spores in all the 
sporangia of the Myxomycetes. All parts-are kept moist with water till they are 
mature; then the water evaporates, and the wall of the sporangium dries up and 
opens in various ways to release the spores. The mode of dehiscence is generally 
very irregular ; the wall as it dries becomes brittle and breaks up into small pieces at 
the least touch or quite of iis own accord. This is the case in almost all the Physareae, 
and in Fuligo, Spumaria, Stemonitis and others. In the Cribrarieae the portions of 
the membrane which have not been thickened fall to pieces, the thickened portions 
remaining as a delicate lattice work. The rind in Lycogala and Reticularia tears 
irregularly and perhaps spontaneously at the apex. In Chondrioderma floriforme the 
outer layer of the wall of the sporangium splits from the apex into stellately diverging 
lobes. In Trichia, Hemiarcyria and Arcyria the dehiscence and the extrusion of the 
spores is assisted by the expansion of the capillitium caused by desiccation, and in 
the first genus by the hygroscopic movements also. The wall either opens spon- 
taneously by an annular fissure in the lowest part of the sporangium, as in Arcyria 
punicea and A. cinerea, or in the upper part as in Hemiarcyria rubiformis, or by 
irregular fissures (Fig. 192 a, 6) either spontaneously or when subjected to a slight 
amount of violence. The various monographs must be consulted for further details. 
The ripe spores vary in size in the different species, their diameter being about 
5 # in Lycogala epidendron and 15 » in Trichia chrysosperma. In many species 
single abnormally large spores often occur amongst the typical ones. They are 
