297 



2. Externally coloiecl black. 



a. Sti'oma scant, composed of large peritlieeia which are almost 

 solitary, or contlnciit in variously shaped, thiu-crusted patches. 

 1. II. effusimi. 



b. Stroma thick or thin, in more or less effused patches 1/2 to 

 1 or 2 cm. long and wide. (Some very convex forms might 

 be mistakenly placed under III.) 8. H. multiforme. 



J. Stroma globose oi sul>gloljose. 

 A. Externally colored not black. 



1. Stroma glol>ose. 



a. Substance of stroma concentrically-zoned, radiate-fibrous, 

 '<pores s microns long or less .0. //. Howeiamim. 



h. Substance of stroma homogeneous, spores more than 8 mic- 

 rons long 10. II. coccineum. 



c. Substance of stroma scant, perforate or granular, ostiola 

 white-margined *6. H. perforatum. 



2. Stroma depressed-imlvinate or rounded, surface dark purple. 



11. II. fuHCum. 



P.. Externally colored black. 



1. Peritlieeia annulate-truncate. 



a. Stroma laige. with the small (.5 mm.) perithecia deeply 

 and evenly sunk in the substance of the stroma so that 

 scarcely more than the di.sk projects, giving a rounded, 

 even appearance 12. II. marginatum. 



b. Stroma of medium size and irregular from the large (2/3-1 

 nun.), prominent perithecia, many of which project one half 



their length beyond the surface of the stroma 



13. II. annulatum. 



2. I'erithecia not annulate-truncate. 



a. Stroma scant, perithecia large, solitary or confluent in 



small, elongated areas in grooves of the bark 



I'l. H. sassafras. 



b. Stroma roughly sultgloliose, composed of a few loosely- 

 aggregated perithecia (I'sually not over 15 or 20 in a 



* n. perforatum is sometimes found with the effused form of stroma, and again 

 with a subglobose or hemispherical stroma. In order that the student may not be 

 at a loss to know where to place it In case he should have only the one or the 

 other form, the key has been arranged so that this species will run under either the 

 effused or the globose group. 



