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growtli from ti very miscroscopic, one-celled body, Avhicli we know « 

 as a spore. V>y some means the spore reaches a place in the 

 bark of tlie chestnul, where conditions are favorable for its 

 growth. Its growth is not essentially different from that of the 

 spores of other fungi. It consists mainly, or principally, of a 

 threadlike growth coming from the spore. This threadlike growth 

 branches, and finally we have a great mass of threadlike fila- 

 ments. In the case of the chestnut disease, the spore may gain 

 entrance at some point, say here, or some little break here, i)os- 

 sibly (indicating on slide), and perhaps occasionally without any 

 break at all in the bark. The growth in the I)ark continues to in- '« 

 crease in size, that is, the general area of the growth, and sooner 

 or later, the same as in practically all plants, we have a fruiting 

 stage of this fungus. This view shows some of these fruiting 

 stages, as we ordinarily see them on the chestnut. Some of the 

 stages, which are not quite so common, will be shown a little 

 later; but I want to call your attention to the fact that, from this 

 point to the point away over there (indicating) we have an area 

 of disease. As a rule the bark in the smooth-barked limbs is 

 somewhat sunken, where the limbs are two or more inches in di- 

 ameter. "Where they are below that diameter, the diseased area 

 may be an enlargement rather than a depression in the bark. 

 These little yellowish spots Avhich you see all over here, many of 

 them, are smaller than the head of a pin. They are of various 

 colors, but usually some tint of yello^\ish brown or orange, or 

 sometimes they weather to a darker color. Those pustules are 

 what we know as the fruiting pustules of this fungus. TJiese 

 pustules, during the growing season, in (lie summer as a rule, 

 produce a certain type of spore, and later in the season, or at a. 

 later stage in the age of the disease, at least another type of 

 spore. For convenience we will speak of tlie first type as the 

 summer S})ores and those of the laler stage as the winter spores. 

 No. 2. This shows a similar branch with a lesion, which has 

 started evidently from around this old dead stub, and this has 

 spread until we get the diseased area from this point, from here 

 probably, (indicating) up to the top of the picture. Now dur- 

 ing the summer, or rather after a rainy spell which is followed 

 by a dry spell, perhaps two days or one day or three days after 

 the rain has ceased, we shall find that these pustules, or fruiting 



