294 



color of the stroma. But this is not entirely satisfactory, because these 

 characters are not at all constant in a great many species. Specimens of 

 a certain species may be found at one time which sliow tlie effused form 

 hi a very marked degree. Again specimens of the same species may grow 

 in a globose or hemispherical form with scarcely a sign of the effused 

 nature. Similarly the color of the same species may vary greatly under 

 different conditions of growth and with increasing age. 



In any given species perhaps the spore measurements are the most 

 constant of any of the characters, and even these vary within certain 

 limits. But the differences between the .spore measuiements of all tha 

 various si>ecles are not of wide enough range to be of any great advantage 

 in throwing them into groups which would be usable in a key. It is true 

 that there are a few sjjecii's here and there which might lie thrown out 

 upon the basis of spore size, but the great ma.iority of them range so 

 nearly together that it is not feasible to attempt a key upon this basis. 



Since it has Ik'cu our (inal pui'pnso to make a key which could b9 

 used chiefiy in the field without the u.se of the microscope, we have deemed 

 it best to follow, for the most part, the example of former writers. There- 

 fore the more evident, although more superficial and unstable characters 

 have been employed, and the key has been based tn a large extent upon 

 the form and e.xtemal cniur of the stroma. Although in a few of the ulti- 

 mate divisions spore measurements have been used, it is hoped that in 

 most cases the student will be able to locate any of the species covered 

 by this key, by means of the naked eye, aided, perhaps, only l)y the hand 

 lens. 



I'ei'liaps not the least valualih' .-lid in identifying species may l)e found 

 in the accomiianying figures. When working with oltjects wliicli are of 

 such a uniformly dark appearance and wliieh show such little contrast 

 between stroma and substratum as do most of the Ilypoxylons. it is no 

 easy task to i)roduce photographs which show their form and external 

 ajipearanee to good advantage. The figures ai)pended are from photo- 

 graphs which wer(> taken near a west window with the rays of the after- 

 r.oon sun falling directly ni)on the .sijecimens. It is the experience of the 

 writer that this gives more contrast and makes the stromata and the 

 perithecla stand out more prominently in the iiliotograpii than is the cas^ 

 \Ahen the exposure is made in diffused light. 



Sixteen species have been collected thus far and the key has been 

 made to fit the specimens at hand without regard to any others. 



