PHYSARELLA MIRABILIS PECK AND STEMONITIS FUSCA ROTH 275 
remained to continue the culture. These developing sporangia were 
fixed in various stages of development in the Flemming-Strasburger 
medium solution, and stained principally with Flemming's triple stain. 
The development of sporangia in cultures usually began during the 
afternoon and was completed by the following morning. Some little 
variation was observed as to the hour of maturity of certain fruiting 
groups, due possibly to somewhat unusual conditions of light, heat, or 
moisture. It was curious, however, to note that the various forming 
sporangia of a group developed almost simultaneously, in spite of 
the fact that all connection between them was early lost, and that 
some were at the edge of the water in the bottom of the jar, while 
others were formed on higher and apparently much drier portions of 
the wood. Mature sporangia were, however, perfectly normal in any 
case. 
Capillitium Formation in Physarella mirabilis 
A mature sporangium (see figure 15) in this species contains a large 
number of more or less branched capillitial threads radially arranged. 
These threads are smooth, except for an occasional small spinous pro- 
jection, and at first glance appear solid, except where they broaden 
out to constitute a lime knot. These knots are numerous, and vary 
in size from that of a barely perceptible swelling in a capillitial thread, 
to large spicules extending from side to side of the sporangium. 
When the plasmodium first begins to form lumps where sporangia 
are to occur, the protoplasm presents no essentially different appear- 
ance from that of the vegetative stage, save that much of the extran- 
eous substances has been extruded and left along the somewhat slimy 
trail; the same bubbly appearance is presented. Before long, how- 
ever, spaces appear in the protoplasm, into which waste substances, 
largely lime granules, are excreted. In sections of the protoplasm as 
it becomes more finely granular, fine tubes can be detected, sometimes 
connecting the knot spaces with the exterior, and sometimes without 
any perceptible attachment to a developing lime knot. The membrane 
surrounding the tubular opening is continuous with the membrane 
surrounding a knot space, if any of the latter be in connection with 
this opening. 
Such a condition is shown in figure i ; the lime knot and capillary 
tubules connected with it are bounded only by a plasma membrane 
continuous with the membrane at the external surface of the proto- 
