DISEASES OF PLANTS. 247 



Hollow potatoes, G, Massee (Roy. Bot. Gard. Keiv, Bui. Misc. Inform., 

 J!)08, \<). J, i)t). 139, I'lO, fig. 1). — During the past autumn some diseased pota- 

 toes were submitted to Kew for investigation. The potatoes were well grown 

 and externally showed no trace of injury, but when cut open were found to be 

 hollow, only an external shell, varying from a quarter to half an inch in thick- 

 ness, remaining. In some specimens the cavity was empty, dry, and lined with a 

 shriveled mass, while in other cases the cavity was more or less filled with an 

 unpleasant smelling pulp, which on examination was found to be teeming with 

 nematodes. A series of sections showed that the nematodes gained entrance 

 to the tuber through the original point of attachment to its branch. They then 

 gradually used up the substance of the tuber, working from the center out- 

 ward until their progress was checked by. the vascular zone, which lies at 

 some distance within the pottito. 



The nematode appears to be Aphelenchus pyri, a species originally found in 

 decaying pears. It is believed to be a wound parasite that gains entrance 

 through the minute openings formed by the decay of the tissue at the jjoint 

 where the vascular ring enters the tuber. 



Experiments in infecting tubers were carried on, and where the slime 

 described above was placed on the scar formed by the detachment of the tubei-, 

 the tubers when cut open after 10 days revealed cavities an inch in diameter. 

 In a second experiment where the nematodes were applied to the eyes of the 

 tubers no infection took place. 



On the existence of Myxomonas betae, F, C. voN Faber {Ber. Deut. Bot. Ge- 

 selL, 26a (1908), A'o. 2, pp. 177-182). — A careful study has been made of the dis- 

 eases of beets which, according to Brzezinski, are due to M. betw. The author 

 claims that he was unable to discover any organism resembling in any way that 

 described by Brzezinski, and he concludes that there is no myxomycete associ- 

 ated with these diseases of the beet. 



The distribution and control of cucurbit mildew, G. KoCK and K. KOR- 

 NAUTH {Ztschi: Landw. Versuchsw. Osterr., 11 (1908), No. 2, pp. 128-1^5, pi. 

 1). — An attempt has been made to determine the extent to which the cucurbit 

 mildew (Plasmopara cubcnsis) is present in the principal regions of Austria, 

 the relative resistance of varieties, and means for the control of the disease. 



The mildew was found quite common in all centers where cucumbers and 

 other cucurbits are extensively grown. Marked differences were noted in the 

 susceptibility of cucumbers, melons, and squashes, cucumbers being much 

 more subject to attack by the fungus, the others seeming to be protected to some 

 extent by their stronger leaf structure. 



Experiments were made with about 70 varieties of cucumbers and marked 

 differences in susceptibility to mildew were observed. All the varieties of 

 c]iuil)ing cucumbers proved quite resistant. 



In experiments for the control of the disease, soil sterilization was found 

 worthless, but frequent spraying with a 1 per cent solution of Bordeaux mixture 

 reduced the amount of loss very materially. The addition of potassium per- 

 manganate to the Bordeaux mixture was found to be without any particular 

 advantage. Rain and a sudden falling in the temperature were found to favor 

 the rapid spread of the mildew. Where cucumbers are grown under glass, it is 

 recommended that the interior of the house be disinfected with formaldehyde 

 before planting and the plants protected with Bordeaux mixture during the 

 growing season. 



Infection experiments with, cucurbit mildew, G. M. Reed ( Trans. Wis. Acad. 

 ScL, Arts, and Letters, 15 U907), pt. 2, pp. 527-5^7). — Experiments were car- 

 ried on with the mildew of cucurbits (Erysiphe cichoraccarum) to determine 



