140 



SYSTEMATIC BOTANY. 



This sclerotium usually begins in the spring a new growth ; 

 liltle branches are produced, each with a globular head 

 (Fig. 254, J), in the cortical region of which the numerous 

 flask-shaped perithecia (Fig. 254, II, III) are produced. 

 The elongated asci (Fig. 254, III) bear attenuated spores 

 (Fig. 254, sp), which germinate and produce the mycelium, 

 which, in turn, infests the young ovaries as before. The 



Black-Knot (Sphaeria morhosa) is another common and 

 injurious Fungus of this order. 



3. Lichenes. The Lichens (Figs. 255, 256) are consid- 

 ered by most botanists to be ascomycetous Fungi, although 

 formerly they were held to be an independent, isolated 

 group. The tissue consists of an aggregation of colorless 

 jointed hyphse, which, in the cortical portion, are usually 



Fig. 254. Claviceps purpurea (Ergot) ; successive stages in the development of 

 the ascospcres ; scl. Ergot {sclerotium) ; per, perithecia ; A, hyphee ; j^, spores ; as, 

 asci. 



