352 EXPERIMENT STATION EECORD. 



at all or only slightly attacked by disease, although the potatoes were planted 

 in soils in which susceptible varieties would not ha^'e produced a sound plant. 

 Other varieties contained a certain amount of disease, and the majority were 

 either entirely destroyed or produced very few sound tubers. 



Another series of experiments is reported upon in which different soil 

 treatments were tested for the control of the disease, the fungicides used being 

 sulphur, copper sulphate, iron sulphate, Strawsonite, potassium sulphid, etc. 

 In no single plat did the potatoes escape disease, and the number of plants 

 affected was so great that it was not considered worth while to attempt to 

 determine the proportion of affected tubers. 



Another experiment was carried on to determine the value of the process 

 of greening the seed potatoes in relation to the disease. It was found that 

 sprouted tubers when planted in soils infected by the fungus were more liable 

 to produce a smaller crop of tnbers and were more subject to disease than xm- 

 sprouted tubers. 



Some fungus diseases of the prickly pear, F. A. Wolf (Ann. Mycol., 10 

 {1912), No. 2, pp. 113-1.3 'i, figs. 8). — The author has during the past 3 years 

 made a study of the common diseases of the prickly pear (Opuntia lindheimerii) , 

 which is used to some extent in south and southwest Texas as a forage crop. 

 The present report considers the structure, cultural characteristics, and life 

 history of the fungi themselves, also the symptomology and the pathological 

 morphologj' of the prickly pear. 



The fungi most common are stated to be SpJiivrella opuntia;, causing in its 

 conidial stage (called Glwosporimji liinatitm) an anthracnose; Perisporium 

 ivrightii, causing the black spot disease; and Ilendersonia opuntice, causing the 

 sun scald of prickly pear. Several other disease-causing fungi of less destruc- 

 tive nature are mentioned. 



Infection with 8. opuntice takes place only following the rainy season in the 

 spring, causing a serious rotting of the new and tender joints. P. wrightii is 

 the least common and causes the least injury of these three. H. opuntice is very 

 abundant and destructive. Segments of all ages are affected. The mycelium 

 spreads within the epidermal system, closing the stomata and developing its 

 pycnidia from these stomatal plugs. The scalded appearance is due to the 

 development of suberized tissue as protection from desiccation. 



Beet nematodes (Heterodera schachtii), O. Fuchs (Ztschr. Landw. Ver- 

 suclisio. Osterr., 14 (1911), 2Vo. 7, pp. 923-952). — ^An account is given of the 

 author's studies on the biology and control of eelworms which attack beets and 

 several other plants. These are said to be migratory and to be carried far and 

 wide in wet weather by moving water, circumstances which increase the diffi- 

 culties of combating their ravages. The Kiihn method of trap-plants is favored 

 but is said to be subject to the drawback that the larvje remain in the soil to 

 renew the disease thus temporarily checked; Chemical measures have thus far 

 been found ineffective. The plan of heating the soil to the depth usually 

 occupied by the roots to a temperature of 63° C is said to prove beneficial, but 

 subject to such drawbacks as expense, difficulty of application, etc. A brief 

 bibliography is given. 



Tumor formation in sugar beets, K. Spisae (Ztschr. Zuckerindus. Bohmen, 

 36 (1911), Nos. 1, pp. 1-11, figs. 6; 2, pp. 57-72, figs. 5).— This presents the more 

 important results of the author's continuation of previous work (E. S. R., 24, 

 p. 47). The experiments were undertaken with plants in a less advanced stage 

 of development, with a view to testing his assumption, previously stated, that 

 the tumors result from mechanical injury to the roots. 



It is claimed that the attempts to produce the tumors by wounding were 

 successful, that these structures develop from wounds in the cambium, and that 



