288 



Bulletin 239. 



growth and development of the parasite. Spores from the spots on the 

 leaves and stems fall on the pods where, in the presence of moisture and 

 the high summer temperature, they germinate, forming a little sprout or 

 germ-tube, which penetrates the tender skin of the pod (Fig. 105) and, 

 branching in the juicy tissues, gives rise to an anthracnose canker. These 

 first appear as little brown or rusty spots which enlarge and darken until 

 nearly or quite black. The dead tissue dries and settles, causing a little 

 pit or sunken place in the pod. In the center of the spot the spores of 



Anrnracnose Canker 



Anthracnose Spores 

 much ma[\n\[\e(iy^^ 



Bean Pod 

 Cul- Across 



seed Coa^ 



Starcll Grains 



Fig. 105. — Showing the relation of the anthracnose fnngns to the iissncs of the bean. 

 To the left above is a diagram of a section across a bean pod lliroiigh an aii'hracnose 

 canker. The large drawing below is a much enlarged vieiv of a portion of this same 

 section. It is largely diagrammatic. It shows how the mycelial threads of the fungus 

 may penetrate the seed coat and enter the starchy tissue of the seed, there to remain 

 dormant tintil the following season. On the left of the large drawing is sliown a 

 spore germinating and penetrating the epidermis. This germ tube brandies, spreads 

 through the tissues of the pod and so gives rise to a new spot or caiiker. To the 

 right above -is shown a magnified vieiv of some of the spores of the anthracnose fun- 

 gus. One has germinated. {Original.) 



the fungus are now produced in great abundance. They ooze out and 

 pile vip, forming little pink masses easily seen with the naked eye (See 

 diseased pods on cover). These masses of spores are held together by 

 a kind of glue or mucilage which, wdien dry, sticks them tightly to the 

 spot. When a drop of rain or dew falls on the spot the mucilage is at 

 once dissolved, and the spores are set free in the water. At this time 

 any disturbance of the bean plants will scatter these spores in the flying 



