38 



of wood ; Stemonitis ferruginea has been found on dry leaves of 

 oak and beech and on moderately dry dead twigs of hemlock. 

 These forms, when ready to fruit, appear to seek not some par- 

 ticular species of wood or leaf but rather some particular condi- 

 tions, probably of moisture and possibly of light also. 



Gulielma Lister's brief accounts (1922, 1926) of the myce- 

 tozoa collected on two trips of the British Mycological Society, 

 Hadden's (1921) record of mycetozoa at Porlock, and Hagel- 

 stein's (1929, 1930) short notes give one some idea of the mois- 

 ture conditions and of the texture of the substrata on which the 

 specimens were found. Such descriptive accounts of the sub- 

 strata, however, are not numerous. 



There may well be a more or less close connection between 

 vegetative stages of different species of mycetozoa and specific 

 kinds of wood or leaves on which they occur, since it is entirely 

 conceivable that different species may differ in their nutritional 

 requirements. But such seems not to be the case with the 

 sporangia. Didymium nigripes, Leocarpus fragilis, Hemitrichia 

 vesparium, and Arcyria denudata are forms which are very con- 

 stant in the moisture conditions of the substrata on which they 

 occur, but each of these forms appears on a variety of species. 

 The first three species seem to prefer relatively sound tissues, 

 while the last one is found on less sound tissues and frequently 

 on wood which has disintegrated so much that it is almost earth. 

 This indicates that either the moisture requirement or the mois- 

 ture tolerance of Arcyria denudata is higher than that of the 

 other forms mentioned. 



Most general accounts of the life histories of mycetozoa 

 state that at the time of sporangium formation the plasmodium 

 seeks the light and a comparatively dry situation. These two 

 requisites are manifestly unimportant for some forms, since 

 their sporangia are frequently situated in the interior of rotting 

 logs where obviously the light conditions, and in all probability 

 the moisture content, do not change appreciably during the time 

 required to complete the life cycle. At least one species of Lam- 

 prod erma (L. violaceum) and at least one species of Hemitrichia 

 (H. serpula) are sometimes found in such situations. On the 

 other hand, a large number of forms seem to require different 

 conditions for fruiting and for vegetative activities. Apparently 

 very different conditions of moisture are tolerated by various 



