. Fungous diseases of plants, with chapters on physiology, culture methods and technique . r-tion affected, offers an easydiagnosis. Generally there isno accompanying stem injury,but in some cases the troublemay extend to the stem; or,again, it may be found uponthe leaves as an extension of astem affection. Upon the tubersthis fungus develops the well-known dry rot (Fig. 61). Onaccount of the presence of themycelium within the tissues ofthe tuber the cells are killed and the tubers rendered liable tothe ordinary forms of wet rot induced by bacterial action or bymold fungi. The dry rot may caus
. Fungous diseases of plants, with chapters on physiology, culture methods and technique . r-tion affected, offers an easydiagnosis. Generally there isno accompanying stem injury,but in some cases the troublemay extend to the stem; or,again, it may be found uponthe leaves as an extension of astem affection. Upon the tubersthis fungus develops the well-known dry rot (Fig. 61). Onaccount of the presence of themycelium within the tissues ofthe tuber the cells are killed and the tubers rendered liable tothe ordinary forms of wet rot induced by bacterial action or bymold fungi. The dry rot may cause serious damage in the field,yet this damage may be further emphasized or even first madeevident while the potatoes are in storage. In regions which arefavorable no fungous disease may become more quickly disastrous,particularly when it affects the tubers as well as the vines. Fortu-nately it is now feasible to prevent the disease and possible evento stamp it out. Host resistance. For more than half a century the resist-ance of varieties of potatoes to the late blight has received the. Fig. 61. The Phytophthora Disease OF Potato Tubers. (Photograph by F. C. Stewart) 168 FUNGOUS DISEASES OF PLANTS attention of scientists. The early work was remarkable for itstime, but the actual results accomplished lose their value nowon account of the fact that the older varieties have largely dis-appeared from cultivation. Excellent work was done during theearly part of 1870-1880, when Charles Darwin himself becamemuch interested in resistance breeding, 1872-1878. As a resultof the interest which was then established, the various wildspecies of potato growing in South America were carefully studiedwith reference to this point and numerous crosses and selectionsmade. Again, during the past ten years there has been a re-vival of interest in this subject, and to-day the general problemis better understood and the results will probably be more may be said, however, that while many var
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