INTRODUCTION, 
11 
being placed in water ; that which has been lately formed resumes 
the streaming condition in a few hours ; when of greater age it 
requu-es to be kept wet for some days before the movement 
begins; the cyst-walls are then absorbed, and their contents 
coalesce. It frequently happens that parts of old sclerotia are 
incapable of resuscitation, but they afford a pabulum for the 
newly awakened plasmodium, through whose veins the cysts may 
be seen to be carried along and broken up. • The sclerotium of 
Dklymium effusum is sprinkled over with a deposit of crystals 
of lime, and" after being revived the cyst-walls are not dissolved, 
as in Badhamia, but remain as empty hyaline sacs Avhen the 
contents has crept out. The formation of sclerotia in plasmodia 
inhabiting the interior of rotten wood is less easy to follow, 
but it is probably of frequent occurrence. A plasmodium of 
Stemonitis fusca, cultivated from spores in a moist chamber, 
passed into the resting state a few days after it had formed, 
spreading in a single layer of crowded cysts on the surface of the 
glass. This sclerotium was dried and re-wetted, when it revived, 
and the cyst-walls were dissolved ; the cultivation was conducted 
with pure water, with no attempt to supply nourishment, and the 
Plasmodium returned to the encysted condition in about twenty- 
four hours ; it was again dried and again revived, but afterwards 
it reassumed the sclerotium state, from which it could not be 
reawakened. 
The Sporangium and SporopJiore. — The formation of the 
sporangium in the Bndosporece has been minutely described by 
de Bary,* and only a brief notice of the general characters will 
be sufficient here. The plasmodium concentrates at certain 
points and developes into sporangia^ of the variovis forms which 
will be found described in the account of each species; they 
are either simple, though often densely clustered, or they are 
combined into an cethaliuni, a cushion-like structure consisting 
of numerous convoluted or imperfectly-defined sporangia. The 
simple forms are either symmetrical, with or without a stalk, 
or they are unsymmetrical, spreading on the substratum with 
an irregular oiitline, when they are called plasmodiocarps. In 
most cases the shape of the sporangium is nearly constant, 
while in others it is subject to much variation. Two abundant 
species, Physarum nutans and Didymium effusum, may be men- 
tioned as examples of variable habit ; in each of them we often 
find vein-like plasmodiocarps and symmetrical spoi'angia both 
stalked and sessile, resulting from the same plasmodium. It is 
true of the shape of the sporangium, as it is of the size of the 
spores and the form and colour of the capillitium, that though 
a valuable guide, it cannot be taken as supplying a rigid specific 
character, and the want of a sufficient series of specimens showing 
how widely a species may vary, has led to the multiplication of 
names without adequate grounds. 
* Dc Bary, I.e., p. 424. 
