September 29, 1922] 



SCIENCE 



371 



dermieally resulted in 100 per cent, infection. 

 Using this method, four crookneck squash 

 plants were inoculated with mosaic from 

 tomato, and four with mosaic from tobacco. 

 All of these plants became infected. Simi- 

 larly, a tobacco and two tomato plants were 

 inoculated with juice from mosaic crookneck 

 squash leaves and became infected. The num- 

 ber of plants kept as cheeks greatly exceeded 

 the number of inoculated plants. All checks 

 remained healthy. In an attempt to cross- 

 inoculate tomato with mosaic from crookneck 

 squash, by the hypodermic needle method, two 

 out of five plants became infected while the 

 ten checks all remained healthy. In another 

 experiment where mosaic crookneck squash leaf 

 tissue was inserted into the midribs of five 

 tobacco plants, the result was 100 per cent, 

 infection. At the same time five tobacco plants 

 were similarly inoculated with mosaic cucumber 

 tissue and one of the five became infected. 

 These inoculations were made using a sterile 

 flamed scalpel. In order to further check 

 whether or not the inoculations were being 

 made under siterile conditions, healthy leaf 

 tissue was inserted into the midribs of ten to- 

 bacco plants. In addition, 30 plants were kept 

 as checks. No mosaic developed either on the 

 inoculated or on the uninoculated checks. An 

 attempt to inoculate tomatoes with mosaic 

 from catnip, Nepeta cataria, resulted in three 

 of the five plants inoculated becoming infected 

 while an equal number of checks remained 

 healthy. 



The investigations made by the writer with 

 mosaic of the legimies have been mainly with 

 cow pea, Vigna Catjang. Although the cow 

 pea has not been reported susceptible to 

 mosaic, this species has been found susceptible 

 under greenhouse conditions. Symptoms in- 

 clude mottling and distortion of the leaves, and 

 stunting of the whole plant. Inoculation by 

 means of transferring aphis (species undeter- 

 mined) from the mosaic plants to healthy 

 plants was shown clearly that this mosaic is a 

 transmissible disease. Two pots containing 38 

 cow pea seedlings were infested with aphis 

 from the mosaic cow pea plants and were 

 placed in insect proof cages. One hundred per 

 cent, infection occurred in both pots while all 

 checks remained healthy. 



In addition to aphis being carriers of mo- 

 saic, numerous experiments have shown that the 

 mealy bug (Dactylopus sp.) also transmits this 

 disease. This has been found especially true 

 where mealy bugs caused mosaic infection of 

 cow peas and soy beans. Cross-inoculation ex- 

 periments using mealy bugs which had been 

 transferred from mosaic infected solanum and 

 cucurbit plants to healthy cow pea seedlings, 

 have resulted in infection in both cases. . Ex- 

 periments have shown that soy bean plants are 

 susceptible to mosaic from cow peas where 

 mealy bugs served as carriers. Mealy bugs 

 with a portion of the mosaic plant on which 

 they were feeding were transferred to the pot 

 containing the seedlings. The result of an ex- 

 periment in which mealy bugs from a mosaic 

 crookneck squash plant were transferred to two 

 pots containing a total of 33 cow pea plants 

 gave 100 per cent, infection. All checks re- 

 mained healthy. A pot of cow pea plants was 

 inoculated by means of mealy bugs from 

 mosaic infected egg plant and of 38 plants 100 

 per cent, became infected. At the same time 

 aphis from mosaic potato were transferred to 

 another pot containing 36 cow pea seedlings, 

 28 of which developed the disease. Out of 60- 

 plants held as cheeks no case of mosaic has 

 appeared. Mealy bugs were transferred from 

 mosaic infected cow pea to soy bean seedlings 

 with the results that a large per cent, of the 

 soy bean plants developed mosaic. 



Data and observations in the greenhouse 

 indicate that mealy bugs may transmit mosaic 

 to solanums. Two tobacco plants and one 

 tomato plant have thus been infected with 

 mosaic from crookneck squash through the 

 agency of mealy bugs. 



The results obtained indicate that the mosaic 

 with which we are working is inter-transmissi- 

 ble between species of Cueurbitacese, Solanaceae 

 and Leguminaceai. To what degree this will 

 hold true under field conditions has not been 

 determined. Judging from observations, the 

 writer believes that infection with mosaic is to 

 a large degree determined by the growth con- 

 dition of the plant. Experiments testing this 

 point have shown that the optimum condition 

 for mosaic infection is an unchecked, vigorous 

 growth of the plant. Inoculations of mosaic 

 within the Solanaceaj or within the Cuciu'bita- 



