22 IMASS. EXPERIMENT STATION BULLETIN 305 



flowering and foliage, did better in these metal containers than in clay pots 

 on a dry surface. There was no sign of copper injury and a chemical analysis 

 showed no indication that copper had been absorbed by the plant from the 

 copper in the container. 



In other tests of the effect of copper on plants, copper containers did not prove 

 harmful to plants grown in them for a period of 200 days. Neither did solid 

 pieces of metallic copper, buried in the soil in glass tumblers in which three 

 crops of tomato plants were grown over a period of 225 days, have anj' effect on 

 the plants. Metallic copper in powder form, however, proved injurious to plants, 

 the effect varying with the type of plant. In some cases the plants produced 

 yellowish or pale yellow leaves; in others, the plants were stunted and produced 

 few if any new roots. 



Jardinieres are practical coverings for clay pots if they are close-fitting. How- 

 ever, if there is a large air space between the pot and the jardiniere, better results 

 will be secured if this space is filled with moist sphagnum moss. 



An enamel paint is a satisfactory means of making clay pots nonporous. To 

 prevent chipping, the pot should be clean and dry before the paint is applied and 

 the pot should be painted inside as well as outside. 



The ordinary clay pot is not satisfactory unless it is used on a moist surface. 

 For use in offices and living rooms, ,moist sphagnum moss under the pot has 

 proved more satisfactory than either moist sand or sponge rubber. The moist 

 sand apparently withdraws nutrients from the pot, and the sponge rubber allows 

 too much free water to come in contact with the pot, thereby keeping the soil 

 too moist. 



Nutrients, particularly soluble nitrogen, may find ingress or egress through 

 the moist wall of a clay pot. The direction of the flow is determined by the con- 

 centration of the nutrients in the moist medium on which the pot rests. If the 

 medium is sand, the nutrients are absorbed by the sand; if soil, the nutrients may 

 pass from the soil beneath the pot through the pot wall and benefit the plant. 

 Plants that were yellow because of nitrogen deficiency recovered in 10 days to a 

 normal green color after the drainage holes were plugged and the pots were 

 moved from a cinder bench to a bench of soil. Plunging pots in soil undoubtedly 

 increases the feeding range of the potted plant in addition to cutting down water 

 loss by evaporation from the wall of the pot. 



THE CRANBERRY STATION 



(East Wareham, Massachusetts) 



H. J. Franklin in Charge 



Injurious and Beneficial Insects Affecting the Cranberry. (H. J. Franklin.) 



Control of the Cranberry Root Grub (Amphicoma vulpina). Flooding to control 

 this insect, described in the last annual report (Bulletin 293), was tried on another 

 bog this season, the winter flood being let off early in April and the bog being 

 reflooded from May 17 to July 5. The treatment was again highly successful 

 and probably may now be safely regarded as very reliable. 



Pyrethrum Dust. (Dr. E. A. Richmond, employed locally by the Crop Pro- 

 tection Institute, cooperating.) Research work with pyrethrum dust mixtures 

 was continued extensively during the past season. Satisfactory power machines 

 for applying the dust on a large scale were developed by local manufacturers, and 



