Reproduction. At the time of spore-formation, the plasmodium 
comes to the surface of its substratum, sometimes climbing along vari- 
ous supports, and then locomotion ceases. The whole plasmodium 
then forms a single stalked sporangium (spore 
case) ; or it organizes several regions, each of 
which produces a sporangium, the sporangia 
often forming a close cluster (fig. 2). In 
sporangium formation the pulsating advance 
of the protoplasm has been observed, forming 
the hollow stalk and finally the terminal spore 
case, whose wall hardens into a firm sheath. 
Nothing is left of the unused plasmodium 
except a network of tough strands. The 
spore case is exceedingly variable in form FIG. 2 . A group of spo- 
rangia of Stemomhs, arising 
and general appearance, and often within it from a plasmodium on a frag- 
there is organized a network of tubes known ment of wood, showing the 
as the capillitium. In the meshes of this slender stalks and linear 
spore cases, 
network countless spores are formed, with 
cellulose walls, most characteristic reproductive cells of plants. The 
wall of the spore case dries and ruptures, and the hygroscopic capilli- 
tium expands, often carrying up and exposing the spores to dispersal. 
The structure of the sporangium is not always so complicated as the one de- 
scribed, for sometimes there is no capillitium, and sometimes there is no stalk. 
Even the spore case may be lacking, the spores being cut off from branches sent 
out from the stalk. A still greater modification in spore formation is exhibited 
in such forms as the common flowers of tan (Fuligo), in which no distinct spo- 
rangia are seen, but the whole plasmodium and sometimes several blended plas- 
modia become transformed into a cushion-like or cakelike mass, known as the 
aethalium. Within the aethalium the spores are found in irregular chambers, 
which may be taken to represent a confused mass of indefinite and blended spo- 
rangia. 
Life history. In following the life history from spore to plasmodium 
great variations are encountered, for at every stage there is exhibited 
extreme sensitiveness to external conditions. A representative series 
of stages is as follows: From the spore wall the amoeboid protoplast 
escapes and soon develops a single cilium or flagellum, by means of 
which it moves very actively. This ciliated cell has quite the appear- 
ance of certain low animals in structure as well as in movements, and 
it multiplies freely by division. Eventually the cilium disappears and 
the cell becomes amoeba-like again, and in this condition it may mul- 
