1034 RESISTANT l'I<ANTS 



appeared in several parts of the United States (i) and Canada, causing ex- 

 tensive damage. 



As was shown by the work of Kunkel, the union between the plant host 

 and the parasite is an extremely intunate oue, which proves that the form 

 of parasitism under consideration is of very ancient date. 



The disease never assumes acute foim. the destruction of the tissues 

 being neither rapid nor complete, but the process of infiltration and de- 

 struction is slow, and a comparatively long time is required to overcome the 

 resistance of the plant. 



Specimens of the parasite were discovered by L,agerheim at Quito 

 (Ecuador) in 1891. It was not stated, however, whether the disease was en- 

 demic or whether it came from Europe, where it has been known since 1841. 



In the present case the potatoes were native to Peru, coming from the 

 eastern slope of the Andes, the regions of Cuzco and Ollantayatambo at 

 about 10,000 ft. altitude. vSome of the infected tubers were even supplied 

 direct by the Indians residing in a locality lying between the valleys of 

 the Umbamba and the Lucumayo near the Panticalla Pass, at 12,000 ft, 

 almost at the limit of potato cultivation. The presence of European 

 materials in these isolated and remote spots must be set aside a priori : 

 therefore host and parasite would be indigenous to Peru. This hypothe- 

 sis is further borne out by another fact : the spores which develop on the 

 Peruvian varieties are much smaller than those found on the European and 

 North American tubers. Generally the disease is much l^ss severe, so much 

 so that the natives pay no attention to it. In the course of time the host 

 appears to acquire a power of resistance which counterbalances the patho- 

 genic action of the Spongospora. 



Thus two reasons suggest that South America, the place of origin of 

 the potato, also gave birth to S. suhterranea. 



808 - Changes in the Chemical Composition of Rye Seed due to the Action of Certain 



Forms of Fusarium. — See No. 742 of this Bulletin. 



809 - Experiments on Smut- resisting Powers of Different Varieties ofWheat. — von 



PLANTS KiRCHNER O. ill ZeitschHjt fur Pflanzenkrankheiten, Year 1016, Vol. 26, No. i, pp. 17-25. 



Stuttgart, April 22, 191 6. 



The writer has, since 1903, carried on cultivation experiments at Hohen- 

 heim, Germany, with 360 wheat varieties (241 winter and 119 summer vari- 

 eties) for the purpose of studying their resistance to smut [Tilletia tritici). 

 The varieties in question are common wheat [Triticum vulgar e), dwarf 

 wheat [T. compactum), rivet wheat [T. turgidum), hard wheat (2'. durum), 

 Polish wheat {T. polonicum) , <.\)Q\t {T. Spelta). two-grain wheat {T. dicoccum), 

 and one-grain wheat (T. monococcnm). The seed was brought into contact 

 with fresh fungal spores, and sown on the same day with equal areas for 

 each variety ; the young plants were afterwards all given the same care and 

 at the end of the experiment the number and percentage of diseased ears 

 in all the varieties were determined. The majority of the varieties proved 



(i) Sec li. l'"ebruavy iiji6. No. 246. (^'V.) 



RESISTANT 



