280 PROCEEDINGS OF THE AMERICAN ACADEMY. 



Plate 10, show what appear to be arrested forms of this mode of 

 development, all of which have brownish walls. These conditions 

 resemble somewhat the mode of development figured by Zukal ('86). 



About three or four days after inoculation on fresh nutrient agar 

 which contains sugar, there frequently appears a spiral primordium 

 of three or four turns, as shown in Figures 1-6, Plate 10, which 

 divides into cells from which short secondary branches are produced, 

 or other cells are formed by gemmation, so that eventually the spiral 

 is enclosed by them. The cells of the spiral enlarge and usually lose 

 their characteristic form. The lateral walls of the superficial cells 

 adhere firmly together, so that eventually there comes to be one to 

 four (sometimes as many as ten) large central cells, surrounded by a 

 cortical layer of empty and often colorless cells (Figures 10-11, Plate 

 10). The development of the spiral may be checked at nearly any 

 stage of its formation and thus certain variations in the form and 

 number of the central cells of the bulbil may result. This variability 

 in the formation of the spiral seems to be largely due to the character 

 of the medium which, when fa\orable, usually produces quite regular 

 primordia with the maximum number of coils, while under less favora- 

 ble conditions, or after the substratum has been once run o\er with the 

 hyphae, many variations are found. Some of the spirals are loosely 

 coiled (Figures 1-2, Plate 10), while others are close and compact 

 (Figures 4, 6, Plate 10). Although the primordium usually loses its 

 spiral form early in its development, it is occasionally foimd surrounded 

 by an irregular layer of cells, as shown in Figure 8, Plate 10. These 

 bulbils resemble somewhat the primordium of a perithecium, like 

 that of Melanospora as shown in Figures 5-6, Plate 3. On account 

 of this resemblance an effort was made to induce them to develop into 

 some perfect form, but although many and varied kinds of experi- 

 mentation as to media, moisture and temperature, were tried, all 

 efforts proved unsuccessful. 



There are also associated with this bulbil spherical or slightly ovoid 

 conidia, on bottle shaped sterigmata, identical with those found in 

 connection with the melanosporous forms. These conidia, which 

 frequently appear on conspicuous white tufts of hyphae scattered 

 over the surface of the substratum, may be formed indi\idually, in 

 chains, or occasionally in a moist atmosphere may cohere at the ends 

 of the sterigmata in a spherical mass. Although, as a rule, the 

 sterigmata occur laterally on the walls of the hyphae, they are often 

 found clustered on irregularly swollen branches and exhibit all the 

 variations referred to below in connection with P. aspcrgiUifnrmis, 



