336 



or pycnospore. A spoi'e arises as a swelling at tlie tip of the stallv which 

 bears it and after it has reached a certain size, is cut off by a septum. 

 Spores vary in color, size, and shape. When young they are hyaline, later 

 becoming greenish, and when mature are brownisli. They may or may 

 iiot become septate ; just what determines tliis is not understood. One- 

 celled spores in some cases develop two-celled spores in culture. The 

 sporophore is binucleate (Fig. 4) and as the swelling begins at the ter- 

 minal end, one nucleus passes into the swelling. About this time, a con- 



Fi^. 5. PiDtomiCro^rapa i). a py,-.ii.lij.ii in m.'.li.in s,'.-.ii)n, dcvflope 

 artificial inoculation. Note the absence of an ostiole. 



m fruil of appL- by 



striction bi'gins to appear a short distance from the spore-end of the 

 stalk. This marks the line of detachment of the si)ore from the sporo- 

 phore. Further develii]iMient (annot be given at present, except to say 

 that the mature spore is binucleate. The most noteworthy difference in 

 size of spores is that they are larger on fruit and in culture than on 

 limbs or leaves. There is also slight variation with host-plants. 



Spores readily germinate in water (Fig. 0), about six liours being 

 required, though we have observed germination after three hours. The 

 tube first appears as a slight swelling at one end or the side. Two-celled 



