283 



Bulletin 145. 



general leaf tissue, gj / is a section through the hollow mature fruit 



body, or pycnidium, con- 

 taining the countless 

 spores. Each spore was 

 originally borne on a little 

 pedicel, or basidium, which 

 seems to grow out from 

 the wall. When the pyc- 

 nidium is ripe, water is 

 absorbed, and these masses 

 of spores ooze out of the 

 mouth of the pycnidium 

 in a long horn-like pro- 

 jection, very dark in color. 

 Here, then, they are at 

 the surface ready for dis- 

 semination. With suitable 

 conditions of moisture 

 they germinate readily 

 upon other pear leaves. 

 Some germinating spores 

 highly magnified are shown 

 in figure 165. The germ 

 tubes arise from either end 

 (c and d), or from the 

 middle (a, b, e and f) of 

 the spore, and readily 



.penetrate the tissues of the leaf for the final production of another 



leaf spot. 



164. — Culture 0/ the leaf spot fungus on pods and 

 stems of bean. 



cultures. Here the fungus grew slowly at first, producing after several 

 weeks tlie pycnidia of the Scptoria, After several transfers this fungus 

 grows quite luxuriantly on bean pods or stems, as seen in figure 164, pro- 

 ducing the pycnidia in a short time, and the pycnidia are then not so defi- 

 nite in form but formed of a very loose stromatic mass. The submerged 

 liyphse are dark in color, while the aerial growth is dense and white, except 

 the stromatic mass inclosing the pycnidium. I have had cultures for eight- 

 een months; and although they have been subjected to various climatic 

 conditions, nothing of further interest has as yet come from them. In 

 nature the fungus is being closely watched for other stages, but I cun say 



