66 MISSOURI BOTANICAL GARDEN. 



the tissues of keartwood of pine, oak, ash, or similar 

 woods in artificial cultures, which fact coincides with the 

 observation that in nature, for some reason, the same 

 thing happens, the older discolored heartwood being 

 usually free from attacks by the mycelium. 



Conidia. 



The conidia are borne on erect or slanting hyphae which 

 branch alternately from the mycelium. They develop 

 terminally in branched or simple moniliform short chains 

 which are often in whorls (pi. 4, f. 5). They are de- 

 tached by the least movement, and in moist air fall 

 together in agglutinated masses about the terminus of the 

 hyphae, in a form which superficially resembles Cephalo- 

 sporium (pi. 4, f. 6). These masses, however, are net so 

 regular as the masses of conidia in the heads formed by 

 Cephalosporium. The conidia bear some resemblance 

 to those of Ovularia. The Cephalosporium^Yike clus- 

 ters are always present in agar cultures after a few 

 days' growth. The conidia vary from obovate to elliptical 

 or cylindrical. They measure from 8/u. to 12/i in length, 

 and from 2/j, to 4/a in width. They are hyaline Avhen 

 young, but often become vacuolate or guttulate when old. 

 They are unicellular and borne on septate hyphae which 

 are from 3/t to 5/x in diameter. Only hyaline filaments 

 bear conidia. In germination the conidia send out terminal 

 germ tubes from either end (pi. 4, f. 7). 



Perithkcia. 



The first indication of the formation of perithecia on the 

 mycelium is the union of two or more filaments and the 

 formation of a knotted mass. The adjacent mycelium 

 changes first to a light brown color, and later to a very 

 dark brown. In the center of the mass the young peri- 

 thecium develops first as a globular black body, without a 

 beak or neck. 



The walls of the perithecium are usually formed by one 



