INJURIES INDUCED BY PLANTS 



101 



FlG. 47. Cortex with stromata, 

 which at a are covered by the 

 periderm ; at b the periderm has 

 been removed ; c shows the cross 

 section of a stroma ; magnified 

 five times. 



and the openings of the perithecia (Fig. 47, a). When the peri- 

 derm is removed, the stroma appears in the brown cortex as a 

 dark brown mass of tissue (Fig. 47, b}. If a section be made 

 of the latter (Fig. 47, c\ a black 

 line will be perceived which sepa- 

 rates the tissues of the cortex 

 from those of the fungus. For 

 each of the openings that appear 

 at the surface one will generally 

 recognize three perithecial cham- 

 bers in the stroma. 



If a section is made at right 

 angles to the stroma so as to 

 expose the longitudinal view of 

 the aperture of a perithecium 

 (Fig. 48), it is seen that the 

 bounding line consists of dark 

 brown mycelium (a), which, be- 

 ginning beneath the surface of the dead periderm, separates 

 the whole stroma from the cortex, and even traverses the 

 outermost sclerenchymatous bundle (b). The tissues thus 



enclosed consist of de- 

 composed cortex and 

 a large quantity of 

 mycelium. The flask- 

 shaped perithecia unite 

 at d to form a common 

 neck, the aperture of 

 which breaks through 

 the periderm. In the 

 outer layers of the cor- 

 tex (c) close beneath 

 the periderm are the 

 gonidiophores, which 

 disperse numerous go- 

 nidia by abstriction. 



The gonidia are sickle-shaped (Fig. 49, a), while the ascospores 

 that are produced in the perithecia are bicellular and provided 

 with peculiar filamentous appendages (Fig. 49, b}. Three such 



FIG. 48. Cross section of a stroma. a represents 

 the bounding zone consisting of mycelium; b, the 

 sclerenchymatous strands ,of the cortex ; c, the 

 gonidiophores ; d, the point where several peri- 

 thecia unite. 



