276 PROCEEDINGS OF THE AMERICAN ACADEMY. 



which are cut off short basal cells which assume a spherical form, 

 become swollen and may produce other branches similar to the primary 

 ^nes. This mode of development is illustrated by Figures 20-24, 

 Plate 6, and Figures 18-19, Plate 9. Instead of the enlarged cells 

 producing branches, however, other cells may arise laterality from 

 them by gemmation, become spherical, and may in turn gi\^e rise 

 to others in a similar fashion. In either case the lateral walls of 

 adjacent cells eventually adhere firmly, thus forming a compact 

 group, each cell of which is almost spherical at first, but later be- 

 comes irregular. The further multiplication of the peripheral cells 

 is subject to considerable variations. Not infrequently the primary 

 or secondary branches, owing to local variation, grow much faster 

 than others and thus produce more cells in that region of the bulbil. 

 If there are several of these points of special activity, the mature bul- 

 bils may be quite irregular in outline. Occasionally a bulbil is formed 

 from a single lateral l:)ranch (Figures 28-30, Plate 8), new cells being 

 formed by a process of budding or by short branches as in the other 

 cases. Ordinarily, at maturity, they are more or less spherical or 

 somewhat elongated, their margins roughened by projecting cells 

 (Figure 20, Plate 9) and are very variable in size, sometimes as large 

 as 350 IX in diameter. There is no differentiation between the inter- 

 nal and external cells as far as contents are concerned. The central 

 cells are, however, as a rule, larger and more angular. 



Papulospora irregularis n. sp. 

 Plate 9, Figures 11-17. 



Mycelium white, more or less procumbent; bulbils hyaline, be- 

 coming light straw-color, somewhat spherical (140-170 /x in diam.) 

 to irregular in outline (250-300 ^t in diam.), margin very uneven; 

 primordium a group of intercalary cells. 



On rat dung, Kittery Point, Maine. 



A pure culture of this species was comparatively easy to obtain. 

 In the hyphae, which are hyaline, procumbent and inconspicuous, 

 certain intercalary cells become enlarged and, by a process of budding, 

 these give rise to other cells which in turn may produce still others. 

 Sometimes short lateral branches are produced, the basal cells of 

 which enlarge and take part in the formation of the V)ulbil (Figure 15, 

 Plate 9). The young bulbils are colorless, covering the substratum, 

 but in older cultures they turn light straw-color. They are usually 

 somewhat spherical in form, measuring 140-170 /U in diameter, but 



