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 CXXII. 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 aelhalium, as Rostafinski 

 understands that term, which is formed from large combinations of plasmodia. 



i. 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. 

 It is either a structureless hyaline and 



FIG. 189. Didymium squamulosum, A.S. (D. . . -r-v 



itucofus, FT.) A ripe sporangium divided longitudinally sometimes, as in Diachea and some species 



near the middle with the spores removed. Magn. about i i i 



a s 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 Lieea 

 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, 



