34 MASS. EXPERIMENT STATION BULLETIN 378 



percent, rotenone 0.75 percent, flour 5 percent; balance clay or talc); Cop- 

 per Hydro Dust E (copper 8.8 percent, rotenone 0.75 percent) ; Lab 789 

 (copper zeolite to make 5 percent copper, calcium arsenate 10 percent, 

 flour 10 percent, balance talc). 



Dormancy of Gardenia Plants. (L. H. Jones.) A group of the Belmont 

 strain of gardenias suddenly became dormant in the early autumn. The 

 dormancy was characterized by a dark, dull green color and a cessation of 

 growth. Passing the hand quickly through the foliage gave a sound as 

 if the leaves were of paper. Attempts to break dormancy by extremes of 

 temperature, high and low (55° F. to 90° P.), of both air and soil failed. 



Of these dormant plants, more than half were infected with Phomopsis 

 gardeniac, causing gardenia canker. The plants were to be used in experi- 

 ments concerned with an investigation of soil temperature and chlorosis. 

 It is known that the larger-flowered varieties, to which belongs the Bel- 

 mont strain, react more quickly to any treatment affecting growth. These 

 larger-flowered varieties are also more susceptible to the canker disease. 

 In one greenhouse, in a bed of 231 plants, 71 percent were affected with 

 trunk cankers. 



For research work, other than problems concerned with disease, it is 

 advisable to use Gardenia veitchii. 



During the early winter of 1939, bud-drop was not prevalent locally, 

 probably because of an above-normal amount of sunshine in the late au- 

 tumn, which favored continued growth. 



Changes in Root Temperature Cause Plants to Wilt. (L. H. Jones and 

 G. E. O'Brien. Cooperative with Chemistry.) The sudden lowering of 

 root temperature or the rapid increase of air temperature causes plants 

 to wilt. The wilting may be followed by the death of tissue in areas along 

 the margin and between veins. These drought spots indicate that water 

 has been lost from these areas more rapidly than it could be absorbed by 

 the roots. Root media of soil, sand, or water were all equally inefficient 

 in protecting the plant from this type of injury. 



Soybean plants, even in solution culture, wilted and suffered drought 

 injury when the solution was cooled from 70° F. to 50° F. by placing 

 the culture in a water bath at 50° F. However, it was learned that the 

 plants can be acclimated to this low temperature if the temperature is 

 slowly reduced during the dark hours of the night. 



Stimulating Photosynthetic Activity. (L. H. Jones and B. Eames.) 

 Negative results were obtained from tests of a proprietary eosin-like 

 material designed to increase growth by stimulating photosynthetic activ- 

 ity. The tests were made with begonia and geranium plants during the 

 winter, when sunlight is at a minimum and when results would be most 

 marked and most advantageous. Check plants and test plants received 

 equal amounts of water and light. The chemical in solution form was 

 applied weekly to the test plants which, at the end of the period, showed 

 no increase in root development, size of plant, or number of blossoms, 

 as compared with the check plants. 



The Effect of Root Media on Root Structure. (L. H. Jones and B. 

 Eames.) There is evidence accruing to indicate that artificial soil and 

 substitutes for soils alter the root systems of plants. Roots developed in 

 one extreme of media, as sand, will sustain the plant when put into the 



