PHYSARELLA MIRABILIS PECK AND STEMONITIS FUSCA ROTH 279 
mature capillitial thread. Chloroiodide of zinc solution, with which 
they stain yellow, often serves to bring out more clearly the hoUowness 
of these threads. 
Figure 14 is another preparation from a mature sporangium, the 
figure being a surface view of a portion of the sporangial wall. A 
small but definite area is shown densely charged with lime granules, 
while in the surrounding wall are embedded more or less isolated lime 
granules. The larger lime knot undoubtedly corresponds to the knots 
shown in section in figures i and 11. The darker spots in figure 14 
represent aggregations of 3^ellow coloring matter. It may be noted 
here that the plasmodia of Physarella mirahilis are bright yellow; the 
hollow stalk of the mature sporangium is reddish; while the spore 
bearing portions are, to the naked eye, grayish-yellow. Each lime 
granule in a knot or in the sporangial wall has also a yellowish tinge, 
and this color seems to dissolve out in water, leaving the granules 
nearly colorless after a time. The capillitial threads also have a 
yellowish cast when viewed under the microscope. 
Figure 15 is a partially diagrammatic drawing of three-fourths 
of one of the mature, somewhat funnel-formed sporangia, on its hollow, 
cylindrical stalk, showing the relation of the various parts. 
The Capillitium of Stemonitis fusca 
While the work on Physarella was in progress, fruiting material of 
Stemonitis fusca was collected from one of the cultures. It was not 
long after the emergence of the white plasmodium from the interior 
of the wood, that a heaping up of the protoplasm occurred, defining 
the sporangial groups. Complete development from the first appear- 
ance until maturity occupied only the tw^elve hours from noon to 
midnight. About two hours after the sporangia in the fruiting groups 
had attained their typical size and shape, the brown tint of matuiity 
was apparent. 
The classical example of the so-called solid capillitium is that of 
Stemonitis. The arrangement of the intricate system of capillitial 
threads in this species is a familiar picture. The hollow stalk continues 
as a central columella to the very summit of the sporangium. From 
this columella branches off at right angles a profuse system of rather 
coarse, branching threads, which terminate sub-peripherally just within 
the fragile, often evanescent sporangial wall in a delicate, anastomos- 
ing, capillitial sac. 
