46 ASCOMYCETES 



pears as a destructive disease in many parts of the country oc- 

 casionally destroying entire orchards. The mycelium of the 

 fungus spreads itself within the interior of the young branches and 

 manifests itself by the formation of elongate gray-brown or black- 

 ish deformities which give the name to the fungus. These some- 

 times attain a length of five or six inches. In the spring these 

 are covered with a velvety surface which is made up of a series of 

 short thread-like hyphae bearing conidia ; these conidia serve to 

 extend the infection to other parts of the tree where they are car- 

 ried. Later the knots are covered with rounded bodies which are 

 the projecting portions of the perithecia mostly imbedded in the 

 stromata ; these contain the ascospores which mature late in the 

 wdnter and escape by a pore at the upper end of the asci. Besides 

 conidia and ascospores two other reproductive bodies have been 

 found but their functions are little known. 



LITERATURE. 



The literature relating to the Dothideales is mostly associated 

 w'ith that of the next order. 



Lindau. Die natiirlichen Pflanzenfamilien, ii : 372-383. 



Winter. Rabenhorst's Kryptogamen Flora Deutschlands, u. 

 s. w. 1 2 : 893-918. 



Saccardo. Sylloge Fungorum, 2 : 588-657 ; 9 : 1004-1053 ; 

 II : 368-379. 



Ellis & Everhart. The North American Pyrenomycetes, 596- 

 621. 1892. 



Farlow. The black knot. Bull. Bussey Inst. 440-454. PL 

 4-6. 1876. 



Order 8. SPHAERIALES. 



The fungi belonging to this order are probably the most numer- 

 ous of all the groups, there being nearly or quite two thousand 

 species known from our own country alone tho many of them are 

 known very imperfectly. They range in habit from leaf parasites 

 to terrestrial forms tho the great majority grow on wood or other 

 vegetable stems. Except in a few families like the Chaetomiaceae 

 the mycelium is chiefly confined to the substratum. 



Some species possess no stroma and the perithecia are either 

 attached to a membranous subiculum or are entirely separate from 



