THE INITIATION OF THE REPRODUCTIVE PROCESSES 191 



were considered to form none until after the first of September. Differ- 

 ences between varieties of plums have been mentioned earlier. 



Differences Induced by Cultural Treatment. — Kirby^''^ notes an earlier 

 differentiation of fruit buds in apples growing in sod than in the same 

 varieties in cultivated soil. Still finer distinctions were noted. 



"The earliest time," he states, "at which flower buds were formed occurred 

 on clover sod, with a low percentage of soil moisture. Flower buds formed 

 earUer on a clover sod than on a blue grass sod having slightly less soil moisture. 

 On the other hand, flower buds formed earlier on a blue grass sod than on a clover 

 sod having about 2.5 per cent, more soil moisture. These facts indicate two 

 things ; first, that the addition of nitrates in the clover sod causes the flower buds 

 to form earlier; and second, that the amount of soil moisture is a very important 

 if not the chief external factor in determining the time at which flower buds form. 



"The formation of flower buds began about the first of July on the plots 

 where it occurred earliest and extended until the middle of September on the 

 plots where it occurred latest, thus occupying a period of about 2>2 months. 

 The time occupied by each tree in forming flower buds was about 4 weeks." 



The time of differentiation in the Baldwin apple in New Hampshire 

 has been found somewhat variable, suggesting the effect of influences 

 proceeding directly or indirectly from weather conditions. ^^ 



Goff^'' supplied water to a 9-year old Gideon apple tree in a dry season. 

 Comparison on Aug. 9 with a similar unwatered tree showed very little 

 difference in the stage of development reached at that time, though buds 

 on the non-watered tree were somewhat more advanced. 



In the sour cherry very strongly growing shoots and shoots partly 

 defoliated by shot-hole fungus were retarded in their development. ^^^ 

 Buds on younger trees were less advanced than those on older trees of 

 the same variety. Since these studies were made at the approach of 

 winter they do not furnish conclusive evidence as to the time of differen- 

 tiation. However, they harmonize with the available direct evidence. 



Abnormalities. — Finally, the occurrence of the so-called second 

 bloom should be noted. Paddock and Whipple^^^ mention a case of 

 this kind. Similar teratological variations reported by Daniel were 

 attributed by him to excessive pruning. This occurrence has been 

 attributed at times to late frosts which destroyed the first blossoms and 

 induced the formation of another set. This may be a correct explanation 

 in some instances. The occurrence of blossoms on the vegetative shoots 

 of several spurs bearing fruit in normal position was noted in an Olden- 

 burg apple at Columbia, Mo., in 1920; the following year the same tree 

 showed this phenomenon in about 20 per cent, of its spurs before any 

 injurious frost occurred. Whether these buds were differentiated the 

 preceding season cannot be stated positively. However, in the Rome 

 Beauty apple vegetative shoots from fruiting spurs were observed to 

 grow to a length of 4 to 6 inches, forming 6 or 7 leaves and then — 

 still early in the season — to open solitary blossoms. In this case differ- 



