74 THE PEACHES OF NEW YORK 



unless it be a few words in regard to the shape. Globose glands are small 

 globes, reniform glands are kidney-shaped. In determining the form of 

 glands examinations must be made several time? in the season, the end 

 of the summer offering the best opportunity and even then care must be 

 taken to secure old leaves. Glands are less variable in adult trees than in 

 trees not yet in bearing. Pomologists for a hundred years have noted the 

 fact that peaches with glandless leaves are very susceptible to mildew. 

 We find this to be the case on the grounds of this Station. This correla- 

 tion between glandlessness and mildew may account for the fact that 

 peaches with glandless leaves are rapidly disappearing from American 

 peach-lists. Wickson says it has been found that peaches with glandless 

 leaves resist leaf-curl.^ 



Gregory has made a careful study of the glands on peach-leaves.^ We 

 publish here the most important facts he brings out. 



" In a large number of cases the glands are stable and can be safely 

 used to aid in the identification of certain varieties. There are also varieties 

 in which the glands are exceptionally unstable, being on the border line 

 between the two types — reniform and globose — and having what might 

 be termed mixed glands. These mixed glands are of two kinds: one in 

 which the majority of the glands are reniform, with some globose inter- 

 mingled; the other in which the globose form predominates. It would be 

 quite possible, as Carriere (1867) suggests, to. distinguish a third type of 

 glands — the mixed type. 



" It is important that leaves shotild be chosen from healthy branches 

 on bearing trees. It is also best to obtain a large number of leaves or to 

 examine the tree carefully before making the final selection of leaves. 

 Mature leaves are best because their glands are full-sized and correctly 

 shaped, while on young leaves the form of the glands is usually obscure. 

 This is particularly true of the reniform glands. On the other hand, old, 

 partly decayed, globose glands frequently have much the appearance of 

 reniform glands. 



" The structure of the glands shows that they are true glands, having 

 an upper layer of long, rectangular, secretory cells that produce a sweet 

 substance, the function of which is not apparent. After the glands have 

 ceased secreting they begin to decay, becoming brown on the upper surface 

 and slowly disappearing until almost nothing is left. This decaying is 

 a very complicated process, being preceded in every case by a suberization 

 and thickening of the cell walls. 



" The spines of the leaf are very similar to the glands in structure, 



' Wickson, E. J. Cat. Fruits 308. 1889. 



2 Gregory, C. T. Cornell Bui. 365:219-220. 1915. 



