36 MISSOURI BOTANICAL GARDEN. 



These tufts of hyphae elongate into a long, round stalk, 



terniinatii 



branches. 



terminating in a bunch of either verticillate or alternate 



Primary Conidia. 



The primary conidia are formed on the upper portion of 

 the stroma or head bv an abstriction of the ends of the 



at 



hyphae (pi. 8, f. 7). They are formed continuously, and 

 as soon as mature, fall away into the mucous mass which 

 surrounds the head. The mass is hyaline at first, chang- 

 ing, as it grows older, to a straw color, and finally to a 

 dark brown. The stalk is usually hyaline in the first 

 stages of its growth, but later becomes almost black at the 

 base, shading off to a light brown near the apex, with a 

 striated appearance. No chlamydospores or sclerotia are 

 formed. At first the stroma is simple, but by the addition 

 of branches from the base becomes gregarious (pi. 8,f. 4). 



The following are the measurements of the mycelial 

 structures: the hyaline mycelium measures from 1.5/* to 

 2.5/* in diameter, averaging 2/*. The colored portion 

 averages in diameter about 4/u.. The secondary conidia 

 measure 3.5/* to 4/* in length, and 1.2/* to 1.5/* in width, 

 averaging 3.7/a by 1.3/x.. The primary conidia average 5/* 

 by 3/*. The stalks average in length from 500/* to 900/*. 

 The head, including the mucous drop, measures on an 

 average 200/*. These do not agree with any previous de- 

 scription of species of Graphium and the fungus is here 

 named Graphium ambrosiigerum , owing to the relation of 

 the conidial stage to ambrosia beetles. 



Cultures were made on a number of kinds of wood. The 

 fungus grew readily in the sap wood of pine, gum, oak and 

 ash, bearing in most cases numerous heads. Secondary 

 conidia are usually formed in abundance. Cultures on the 

 heartwood of these trees produce little or no growth of the 

 fungus. Light colored wood is stained a color varying 

 from a dirty gray to a light brown, or almost black. 



