AN AQUATIC MYXOMYCETE. 69 



The bright black sporangia developed on the completely submerged 

 roots have no perceptible amount of lime on their surfaces ; they are 

 smooth and bright, simply because the yellow network which passes over 

 them is too fine and translucent to materially affect the appearance of 

 the pigmented proper membrane of the sporangium (c. f. figs. 3 — 6). 

 But in the case of the dull greyish sporangia developed on the roots 

 outside the liquid, the dullness is clearly due to the large quantities of 

 calcium carbonate deposited as fine granules and crystalline masses in 

 the outer coat. In some cases the infiltration with lime goes so far 

 that the membrane is quite brittle and cracks into angular pieces (fig. 5), 

 and on the addition of dilute acetic acid the crystalline needles (fig. 9) 

 or granules rapidly dissolve, copious effervescence of carbon dioxide 

 taking place at the same time. These facts suggest the question 

 whether calcium carbonate is not perhaps formed in abundance on all 

 the developing sporangia, but in the case of those submerged in 

 the water it is possibly carried off dissolved in the carbonic acid 

 diffused throughout the solution, whereas in the case of those 

 sporangia developed out of the solution, the surplus carbon dioxide 

 escapes into the damp air around leaving the crystalline solid calcium 

 carbonate behind. 



That calcium carbonate is actually produced in the interior of the 

 submerged sporangia also is abundantly proved by the excreted nodules 

 of that mineral which are contained in the nodes of the capillitium to 

 be referred to shortly ; of course the conditions under which clusters 

 of needles or granules of calcium carbonate are excreted in the cavity 

 of the sporangium might be very different from those referred to above. 

 The capillitium, as shown in fig. 8, is constituted simply of a loose 

 irregular network of delicate horny fibres, which may be either colour- 

 less and nearly transparent, or tinged with the purple-brown pigment 

 so common in other parts of the sporangium (fig. 5). What may be 

 termed the nodes of this irregular meshwork are usually enlarged, and 

 in the triangular or irregularly angular enlargements are deposited the 

 concretions of granules or crystals of calcium carbonate referred to 

 above (fig. 8). The fibres or rods forming the capillitium are apparently 

 solid, and spring from the inside of the wall of the sporangium, their 

 bases being dilated at the areas of attachment (figs. 5 and 8). The 

 fibres pass directly across the cavity of the sporangium in some cases, 

 while in others they seem to terminate freely in it ; or they are 

 connected together, at various angles, with other fibres which cross 



