150 



THE HOP. 



purposes may be looked upon as "seeds," are very small. 

 They soon fall oft' the branch producing them (Fig. 76b), and 

 by their number many thousands in a single mold spot 

 increase the mealy appearance of the affected part. Being 

 necessarily very light, many are blown about by the wind. 

 Under proper conditions of moisture and temperature each 

 one can germinate in a few hours and produce a small 

 thread which fastens itself to the leaf of the hop and begins 

 a new mold spot. We can thus understand how quickly and 

 silently mold can spread in a garden. From one small patch 

 several thousands can arise in a few days by the production 

 and dissemination of these spores by the wind, much as 

 thistles and other weeds may be spread about the country 

 after seeds are produced. The germination of spores, and the 



a 



FIG. 78. SINGLE ASCOCARP. 



&, Burst, showing ascus. a, With its contained ascospores. c, Free ascospores. 

 Highly magnified. 



growth of spawn producing more spores, can be repeated 

 over and over again in a few day?, and it is in this way that 

 the mold spreads during the summer. 



The spores and spawn, such as we have mentioned, are 

 short lived and cannot exist through the winter. The fun- 

 gus, however, in autumn, or when the leaf upon which it 

 is living begins to die, produces upon its body of threads 

 small round cases containing another kind of spore, which 

 has the power of resting during winter, and when fully 

 developed, these round cases (ascocarps, Fig. 77) are dark 

 brown in color, or almost black, and give a rusty appearance 

 to mold spots which have been allowed to develop un- 

 checked, especially those on the underside of leaves and on 



