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 p 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 /u, and their walls are stratified 

 and thick, sometimes 10 /u 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 its 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, b) 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 /n in Lycogala epidendron and 15 /* in Trichia chrysosperma. In many species 

 single abnormally large spores often occur amongst the typical ones. They are 



