31 



spots, have pushed out a little mass, a threadlike mass, in much 

 the same way as you would press out the paste from a collapsible 

 tube by pinching the tube. As a result we get, perhaps, from 

 one of these pustules, anywhere from one to fifteen or twenty 

 structures of that sort, (indicating) which are, of course, here 

 greatly magnified. This represents the pustule at the base, this 

 yellow area; and this is one of the threadlike masses which has 

 been forced out by the swelling of the mucilaginous matter in 

 the pustule. 



No. 3. Each one of those masses shown at the right hand side 

 of the view is composed of many hundreds of thousands of spores, 

 no larger than bacteria. One of these spores may, so far as we 

 know, under favorable conditions, reproduce this fungus and con- 

 sequently reproduce the disease, if it starts growth in the proper 

 place. 



No. 4. This shows simply a somewhat larger view of one of 

 those pustules, from which three of those spore threads have 

 been produced. At the upper part of this picture we have a sur- 

 face view of the chestnut bark in which we find the pustules 

 gathered in the crevices. This is rather characteristic on chest- 

 nut bark that is of a sufficient age to be cracked. Only on smooth 

 chestnut bark, as a rule, do we find these pustules all over the 

 bark. In the cracked bark we find them primarily, if not entirely, 

 in the crevices. 



No. 5. There we have a section of a small branch that shows 

 some of these pustules, and above some of these threads as they 

 appear on the bark of the chestnut. I have nothing special to 

 say about that view, except that, so far as the color is concerned, 

 we are apt to get it just that color, but quite as often somewhat 

 darker, with a little orange or reddish tint to the pustule. 



No. 6. Now if we take one of those areas of disease on smooth 

 bark and cut info it, if we shave the top of the bark off with a 

 sharp knife, suppose we take just such a case as we have at the 

 left here (in fact this is made from the same branch) and shave 

 it so as to show what is beneath, we get a discolored area, a 

 rather characteristic area, which is not shown as well in this 

 view as it will be in another; but remember that this view at the 

 right represents such a branch as that at the left, with the sur- 

 face of the bark removed with the knife. 



