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THE POPULAR SCIENCE MONTHLY, 



pores, just visible to the eye in some species (see Fig. 6 in August 

 number), from ten to twelve thousand occurring per square inch ; others 

 are coarser and not so numerous. Minute as are these pores, their in- 

 terior is studded with the basidia and spores, a few of which, magnified 

 four hundred diameters, are shown in Fig. 15, where a represents 

 sterile cells and b the basidia, usually having four sterigma, each of 

 them bearing a spore.* 



Fig. 14 represents a very interesting but destructive type of fungi, 

 and, in one sense of the word, parasitic upon living trees. It is 

 drawn from Polyporus fomentarius (Fr.), " Dingy-hoof Polyporus." 

 Pileus ungulate, sometimes four to five inches broad, sub-triangular, 

 obsoletely zoned, nodulose, brownish-gray, resembling coffee slightly 

 tinged with milk ; its peculiar form and color make it easily identi- 

 fied. Closely allied to it are Polyporus nigricans (Fr.), Black-hoof 

 Polyporus ; pileus pulvinate ; Polyporus igniarius (Fr.), Rusty-hoof 

 Polyporus ; pileus at first tuberculoso-globose (immarginate) ; Po- 

 lyporus fulvus (Fr.), Tawny-hoof Polyporus. 



The first three are found upon beeches, willows, hornbeams, cotton- 

 woods, and plums, and trees of similar characteristics, and grow upon 

 live trees, where they have been injured by the breaking of limbs, or 

 by the checking of other limbs, at the junction with the trunk of the 

 tree. Polyporus fulvus (Fr.) is found upon the firs. The mycelia, 



Fig. 15. Fig. 16. 



once started, will continue to grow in the heart-wood of the tree, while 

 the sap-wood, with its bark, is still growing. If the wound is not 

 closed by the growing tissue, the decay continues, causing hollows in 

 the trees. These are not uncommon sights to those familiar with for- 

 ests, and the trees almost seem to be conscious that they must keep 

 their bark intact, or the invisible fungi will start and eventually de- 

 stroy their stately proportions. 



* From " Fungi : their Nature and Uses," by M. C. Cooke, M. A., LL. D., vol. xv of 

 the " International Scientific Series. 1 ' 



