EXPERIMENT STATION BULLETINS. 



689 



TABLE XI.— Continued. 

 4. No treatment. (Check.) 



2 "adults. 



SJyoung under different mother-scales. 



98 less than half gro-rni. 

 46 about half grown. 



35 adults. 



I 121 living young, 

 with •! 8 dead yoimg. 



1 142 eggs. 

 One adult 



'oung. 

 eggs. 



had 



/5y( 

 I 6 eg 



The order of efficiency as shown by this table is lime-sulphur, calcium 

 thiosulphate, whitewash — the last named being a little better than no 

 treatment. In case of the lime-sulphur treatment, a greater proportion 

 of the scale-insects were dead after seven days than after fourteen hours. 



Just here, the eifect of the lime-sulphur in softening the wax must be 

 noted. After seven days it was found that in several cases the softened 

 wax on the scale margin had dried and in so doing had become stuck to 

 the surface of the plant so closely as to confine the young with the 

 mother. Under untreated scales, five young and six eggs were the larg- 

 est numbers found; but under some of the scales after seven days treat- 

 ment as many as four eggs, nine living young and twenty-two dead 

 young were found. This showed clearly that in some cases 'the young 

 could not escape but were literally packed under the scale-covering of 

 the mother — sealed in. Such a condition must of necessity bring about 

 the death of all insects "under the scale from over-crowding. 



Many of the scales treated with lime-sulphur and left on the tree 

 from three to four weeks showed the condition represented in Plate II, 

 Fig. 1. It appeared that the lime-sulphur had become entirely oxidized 

 and a white crust stooled up from the scale — especially around the 

 margin of the scale — so that the latter was pughed .loose from the sur- 

 face of the plant and could be easily brushed off. 



The results, fourteen hours after treatment with lime-sulphur, showed 

 again that many scale insects were more or less comatose at first, but 

 revived somewhat after a few minutes in fresh air. They would con- 

 tract, after a little while, upon being touched with a needle point. They 

 revived quicker than specimens that had been kept in pure nitrogen 

 for fourteen hours — but they certainly did appear to revive be- 

 cause fresh air was admitted when the scale was lifted. 



A series of experiments Avere carried out with a dormant apple tree, 

 to determine whether the tree was respiring or whether its bark might 

 be able to furnish oxygen through photosynthesis. 



A small apple-tree was taken from the nursery just after the leaves 

 had been killed by frost in the Fall, and potted. A glass cylinder was 

 fastened around the body of this tree air-tight and arranged so that 

 air could be drawn into' the cylinder or expelled through a two-way 

 cock by means of mercury. The arrangement may be readily under- 

 stood from Fig. 7. By means of the apparatus described under the 

 respiration work with insects, then, it was comparatively easy to de- 

 termine how much carbon dioxide was given off and how much oxygen 

 was used from a certain area of the tree in any interval of time. 



Results of four experiments carried out with this apparatus are re- 

 corded in Table XII. 



