FlORIOA A\n (lAl.Il-OKNIA LABORATORIES 27^ 



were compared \\ ith the results of experiments which determined 

 the acidity of the ciKunihcr juice 



by titr.Uinq ai^ainst N/ 10 caustic soda recently set from N/10 H[ydrogcn] 

 C[h}lLoridc], usinq Phcnolphthalin as an indicator after compar[ing] 

 this with antliocyan, methyl orange, and various other indicators. The 

 juice was obtained in quantity from the parenchyma of ^reen fruits from 

 the market, as many as possible of the large vessels being cut away, 

 [the] rest graded, juice pressed out and at once titrated. Samples, [he 

 found, from the} two ditfcrent sources gave [the] same results. 



Smith wrote into his Ceutralblatt article his observations on 

 the alkalinity of vessels. He hesitated to publish more until he 

 had thoroughly checked the literature to see what already had 

 been written, and to test the matter of alkalinity through more 

 species of the cucurbits. In field research that year, using neutral 

 litmus paper from the Division of Chemistry, he began testing a 

 wide variety of plants to determine their alkalinity and acidity. 

 August 12, in a manuscript of about fourteen pages of rather 

 closely written matter, he announced, " This is the 6th genus of 

 cucurbits tested and the fluid in the vessels of each is strongly 

 alkaline." The point, he believed, was bound up with practical 

 methods of preventing the disease. A quotation will explain: '■* 



The practical method of preventing the disease is to fight the insects 

 that feed upon the vines. Destroy them and you wipe out the disease. 

 At the same time all diseased plants should be pulled and burned, so that 

 the insect shall find nothing but healthy plants to feed upon. 



I seem to hear some one ask: "' If these things are true, why does not 

 every vine become diseased and so it become impossible to grow cucumbers 

 or other cucurbits where the disease exists?" It also happens that I can 

 answer that question. The germ is peculiarly sensitive in certain ways, for 

 example, to dry air. Exposure to direct sunlight for some hours also kills 

 it. Moreover it is sensitive to the acid tissues of the plant and thrives 

 only on alkaline juices. In cucurbitaccous plants the green tissues are acid, 

 while the fluid in the water ducts is alkaline, hence we find it thriving in 

 the water ducts and choking them up, but if it were thrust by an insect 

 bite or otherwise into the parenchyma of the plant it would make a feeble 

 growth and if only a very few germs were inserted they might die. In 

 spite of these circumstances enough plants become infected to carry the 

 disease along and to do great damage to muskmelon, cucumber, and squash 

 fields. 



'* Erwin F. Smith, Some bacterial diseases of truck crops, Trans. Peninsula Horti- 

 cultural Society. Meeting at Snow Hill, Marj-land, January 11-12, 1898, pp. 142-147, 

 at pp. 143-144. 



