92 MISSOURI BOTANICAL GARDEN. 



at the top. The stalks vary in height from 1 to 2 min., 

 averaging 1.5 mm., with an average diameter of 25/*. The 

 heads, when enveloped in mucus, are globular and measure 

 from 40 to 600/* in diameter ; without the sheaths they 

 are flattened oval or fungiform, and measure 30/t to 200/*. 

 They are colorless at first, but later change to gray or 

 green. When a stalk is broken off before maturity, it 

 often sends out small branches, either of single hyphae or 

 of clusters of hyphae, bearing conidia. 



Secondary Conidia. 



The secondary conidia are usually elliptical in shape, and 

 measure 3.6/* by 1.8/*, average. They are hyaline, color- 

 less, and are borne both terminally in close clusters and 

 on simple hyphae, and in a short time fall off and adhere 

 together, thus forming miniature heads (pi. 9, f. 9). 



Primary Conidia. 



The primary conidia are elliptical in shape, and are borne 

 terminally on branched hyphae (pi. 9,f. 10). They meas- 

 ure 3.8/* by 1.6/*, average. They are hyaline and colorless. 

 In some cases, where the upper portion of the stalk or 

 head has been broken off new stalks sprout out from the 

 region of the apex in the old one. Branches are also 

 formed without injury. 



The fungus penetrates deeply into red gum boards, giv- 

 ing them a dirty appearance, rendering them unfit for 

 making the best grade of boxes, crates, etc. It permeates 

 the medullary rays and many of the larger and some of the 

 smaller vessels of the wood. The mycelium in the wood is 

 generally of a color varying from gray to brown or dark 

 green. 



Graphhnn rigidum (Pers.) Sacc. 



A species of Graphium was found discoloring the sap- 



