2o6 



Bulletin 132. 



duced on wilted leaves in a wet season ) ; while b and e show the same fun- 

 gus under normal conditions. I have experienced no difficulty in germina- 

 ting the fungus on plates of agar, and in securing pure cultures in tubes of 

 sterile bean stems or of petioles of celery. In this condition the fruiting hy- 

 phae are often ultimately more than a millimeter in length. At first conidia 

 are regularly produced, leaving the accustomed geniculations ; and these 

 couidia vary in length from some exceedingly short to others measuring 250 /*. 



After the hyphae have attained considerable 

 length no further conidia are produced ; and, 

 instead, the spore-like branches which arise 

 remain attached, and appear as true branches 

 of fertile hyphae. Figure 49 (Leitz ocular i, 

 objective 4) illustrates the character of growth 

 on bean stems. I neglected to make a photo- 

 graph of a good petri-dish isolation culture 

 until it was badly contaminated with bacteria ; 

 but Fig. 50 serves to show the nature of the 

 growth on agar. The colonies are large, circu- 

 lar, at first olivaceous, and not readily separa- 

 ble from the agar. Later a grayish-white aerial 

 growth of cottony mycelium appears, inter- 

 spersed with which are the long fruiting hyphae. 

 In general, growth in artificial cultures is 

 characteristic, both on agar and on bean stems, 

 differing materially from that of half a dozen 

 Cercospons cultivated diuring the past summer. 

 No perfect stage of this fungus has been secured; 

 but every effort is being made to ascertain if 

 there is an intervening perfect form. As j'et, I 

 have not been able to secure cultxires of Cer- 

 cosp07'ce on hosts closely related to the celerj'. 



B. Late Blight of Celery. 

 General Discussion. 



49 



-Hyphae of the Cercos- 

 pora, when grown on 

 bean stems. 



At the same time that the early blight 

 was abundant on the Ithaca flats, a differ- 

 ent disease was found in a garden not far 

 distant. The latter disease had then appeared on a few leaves only. 

 In general appearance it might easily have been mistaken for the 

 early blight, although it is distinguished from the latter by more 

 iiregular spots, which are of a tawny color. Under a hand lens, 

 minute, black, fruit bodies, or pycnidia, could be seen on either 



