26 Bulletin 332 



the brittle outer layer, split or whole, was softened and wrinkled 

 (plate 1, fig. 13) and conld be easily removed. Furthermore, it 

 was noted that in all experiments where crude carbolic acid was 

 used as a spray, especially in strengths greater than 1 per cent, 

 the eggs had an unusually bright shiny appearance after the spray 

 had dried. This glossy appearance indicates that the semi- trans- 

 parent outer layer has undergone some sort of a change. It was 

 also observed that many eggs with split outer coverings treated with 

 crude carbolic acid and cresols shriveled along the meso-dorsal line 

 (plate 1, fig. 14). This type of shrivel which also takes place to 

 some extent with other treatments indicates that the pigmented 

 layer of an egg showing a split outer shell is particularly susceptible 

 to various chemicals. Furthermore, treated eggs with a whole outer 

 covering frequently shriveled in a like manner. This indicates that 

 the outer shell is weakest along the meso-dorsal line and any foreign 

 material which can soften or disintegrate the outer layer would 

 naturally penetratfe this portion of the egg first and cause it to show 

 its early stage of shriveling along the least resistant portion. 



A number of other chemicals were tried and their effect noted, 

 but their mode of attack has not been observed with sufficient care 

 to warrant a statement at this time. Possibly it would be worth 

 while to call attention to the fact that sodium hydroxide seems to 

 react upon the glutinous layer in such a manner as to loosen the 

 egg from the tree and cause it to fall to the ground. At least a 

 large number of eggs were lost in all the experiments with sodium 

 hydroxide. 



A large number of experiments were conducted with various 

 common sprays and other chemicals during March and April, 1917, 

 and the results of the more important of these are recorded in table 

 4. The predominant species of eggs used in the various experi- 

 ments is indicated in the table. In the experiments with A. avence 

 a few eggs of A. sorhi were present, but, so far as is known, these 

 never exceeded 15 per cent of the total number, while in the ex- 

 periments with A. pomi the eggs of A. sorhi ran close to 30 per cent 

 (at least a number of counts of newly-hatched stem mothers gave 

 this approximate percentage). This percentage of the eggs of 

 A. sorhi in the experiments shows that the eggs of this species 

 resemble those of A. avence and A. pomi in their response to various 

 stimuli ; however, there is apparently some difference in the suscep- 

 tibility of the different species. At least there is good indication 

 of this if one compares the percentages of hatch among the different 

 species under similar treatments.. A. avence, is probably somewhat 

 mbre susceptible than either A. pomi or A. sorhi. Another point 

 of interest in respect to susceptibility is the fact that all eggs of 



