290 



GENERAL MORPHOLOGY OF PLANTS 



the cherry mildew, growing on cherry, peach, and apple trees, 

 especially injurious to nursery stock; the rose mildew, lilac 

 mildew, etc. 



Lilac Mildew (Microsphccra Alni). 



438. The conidial stage. This is developed in asexual re- 

 production. Short erect branches arise from the superficial 

 mycelium (paragraph 43 7) which are divided by cross walls into 

 short cells (fig. 233). The branches grow at their base and con- 

 tinue to divide into short cells, raising the older cells farther and 



Fig. 233- 



Willow mildew; bit 

 of mycelium with 

 erect conidipphores 

 bearing chains of 

 conidia; conidium at 

 left germinating. 



Fig. 234- 



Fruit of willow mildew, showing hooked 

 appendages. Genus Uncinula. 



Figs. 234, 235. Perithecia of two pow- 

 dery mildews, showing escape of asci con- sphaera. 

 taining the spores from the crushed fruit 

 bodies. 



Fig. 235. 



Fruit body of an- 

 other mildew with 

 dichotomous append- 

 ages. Genus Micro- 



arther away from the surface. At the same time the older cells 

 swell out somewhat so that they appear like chains of beads, or 

 small barrel-shaped spores or conidia. The older ones separate 

 and fall upon the surface of the leaf or stem, etc., giving a pow- 

 dery appearance. These conidia are carried to other plants or 

 other parts of the same plant, there spreading the disease. 



