264 PROCEEDINGS OF THE AMERICAN ACADEMY. 



one enlarges and usually also the second or third (Figures 29-37, 

 Plate 4). From these, other cells are then produced by budding, 

 the lateral walls of which eventually adhere closely to those ad- 

 jacent, so that there comes to be from two to six large central cells 

 surrounded by a number of smaller ones, all filled with granular proto- 

 plasm, the only apparent difference being in their size. As they 

 mature, however, the inner and outer cells become markedly differ- 

 entiated. The former, which are large with conspicuously granular 

 contents and with numerous oil globules, secrete a thick hyaline wall, 

 while the latter, which become empty and spherical, adhere to each 

 other loosely, their contents probably being absorbed by the central 

 cells (Figure 41, Plate 4). Although the terminal cell is usually the 

 most prominent in producing the larger central cells, j'et one or both 

 of the two adjacent cells may take the lead and, owing to their lateral 

 growth a somewhat crosier-like coil may even occasionally be produced 

 by one or more of these secondary branches. 



Germination of the bulbils. — For the purpose of studying the germi- 

 nation, bulbils in different stages of development were placed in Van 

 Tieghem cells. In about twelve or fifteen da^'s the marginal cells of 

 those that were immature — that is, those whose superficial cells 

 still contained protoplasm — began to send out vegetative branches, 

 one or two from each cell (Figure 42, Plate 4) ; but the central cells 

 were not observed to produce tubes at this stage. x\fter about a 

 month the mature forms begin to germinate, but very sparingly, each 

 of the large central cells usually sends out a single germ tube which 

 readily pushes aside the loosely adhering peripheral cells. The germ 

 tubes or vegetative hyphae, as the case may be, usually divide up into 

 short cells which become swollen w4th the protoplasmic contents and 

 more or less constricted at the partitions (Figure 42, Plate 4). 



The conidia. — The erect septate conidiophores of the so-called 

 VerticiUium agaricinum (lyink) Corda, var. claviscdum Sacc, already 

 referred to, are invariably associated with the bulbils in pure cultures, 

 and are thus shown to be not, as Saccardo supposed, accidentally 

 concomitant but a regular phase of the life cycle. Figure 45, Plate 

 4, shows bulbils and the VerticiUium fructification definitely connected 

 on the same erect hypha. This phenomenon is of so frequent occur- 

 rence that there is no possibility of error. The conidiophores are 

 simple or branched, with the sterigmata in whorls, varying- greatly in 

 number, commonly in threes and frequently clustered at the apex. 



The mature conidia are ellipsoidal to oblong and rounded at both 

 ends, varying considerably in size, the average measurements being 



