THE FUNGI. 



147 



The Black Fungi (Pyrenomycetes) are important plants 

 of this class. Familiar examples of these are the black 

 knots common on Cherry and Plum trees. These plants 

 produce filaments which lie dormant under the bark until 

 the spring of the following year, when they develop rapidly, 

 producing a disease of the branch on which they grow by 

 causing an abnormal de- 

 velopment of the bark. 

 The gonidia formed by 

 the asexual process may 

 be studied on the surface 

 edge of thin sections of 

 the knot made in the late 

 spring ; the ascospores of 

 the sexual process may be 

 studied in thin sections 

 cut in the winter. The 

 spores may then be seen 

 in their sacs, and by the 



FIG. 85. Claviceps purpurea, the Fungus 

 that produces ergot on Rye. A, a scle- 

 rotium or ergot that forms in the heads 

 of Rye, bearing seven stromata or fruc- 

 tifying heads; B, one of these heads 

 seen in section, showing the peri- 

 thecia, cp, which bear the asci; C, 

 a peritheciura containing asci more 

 highly magnified ; D, a single ascus 

 discharging its spores, sp. (From 

 Sachs, after Tulasne.) 



sides of the sacs slender 

 filaments, the so - called 

 paraphyses. 1 



There are many species 

 of Black Fungi. The 

 black spots that develop 

 on the leaves and bark of 



different kinds of trees, 



and ergot, a parasite on heads of rye and other grains, are 



among them. 



References for Reading. Vines' " Text-Book of Botany," pp. 301, 

 302; Bower's "Practical Botany," pp. 481-483; Cooke's "Introduc- 

 tion to the Study of Fungi," pp. 197-220; Bessey's "Essentials of 

 Botany," pp. 163-165. 



1 Have on hand material collected at the different seasons, and pre- 

 served in alcohol or formalin. Arrange Practical Studies. 



