434 SECOND PART.—MYCETOZOA. 
Delay may of course occur where the conditions are unfavourable. That the 
several species behave very differently in these respects is shown by the fact, that 
many of them, Trichia rubiformis, T. clavata and T. varia for example, are observed 
to form their sporangia almost entirely during a short portion of the yearly period 
of vegetation. The biological relations of most of the species require further 
examination. : 
Section CXXI. The structure of the mature sporophores is n all cases 
essentially the same as in the Ceratieae. The ripe sporangia in the majority of the 
endosporous genera, which show a great amount of variation in different species, must 
be described from a few of the typical forms, which have been known for some time. 
For special peculiarities the reader is referred to monographs and especially to 
that of Rostafinski. 
We must first distinguish between the simple sporangium, which proceeds from 
one plasmodium or from a part of one plasmodium, and the aefhalum, as Rostafinski 
understands that term, which is formed from large combznations of plasmodia. 
1. It has been already said that the mature sporangia in most Myxomycetes 
are round or elongated, stalked or sessile vesicles one to a few millimeters high ; less 
frequently, as in Didymium serpula, Trichia 
serpula and Licea flexuosa, P., they are 
cylindrical or flattened tubes forming a 
network and lying on the substratum. 
The wall of the sporangium is formed 
of a membrane which in constitution re- 
sembles the cellulose-membranes of plants. 
ae EE ae It is either 2 structureless hyaline and 
Keen BX), A ripe sporangium divided longitudinally  SOMelimes, as in Diachea and some species 
25 times. of Physarum, an extremely delicate mem- 
brane, or it is thick and firm and evidently 
stratified, as in Leocarpus vernicosus, Craterium, Trichia varia and others; in the 
Physareae included in the old genus Diderma it is even double, that is, it is 
differentiated into two layers which may be easily separated from one another 
and which do often separate of themselves. Projecting thickenings of different 
dimensions in the shape of warts and ridges occur in some cases, on the 
whole of the surface for example of the thick olive-brown outer layer of Licea 
flexuosa, and on the inner surface of the base of the sporangium of Arcyria 
incarnata, A. punicea and A. nutans. The whole of the inner surface of the 
membrane in Cribraria and Dictydium shows projecting thickenings in the form of 
flattened ridges connected together into a delicate net-work. The membrane is 
colourless or coloured in various shades of violet, brown, red and yellow according 
to the genus and species; it is usually continued at the point of attachment of the 
sporangium into an irregular‘ membranous expansion formed of the dried envelopes 
of the plasmodium, and securing the sporangium to the substratum. 
The stalks, except in the Stemoniteae, are tubes usually with a thick wall, which 
is wrinkled and folded lengthwise and is continued above into the wall of the 
sporangium, Its lumen is either in open communication with that of the sporangium, 


