394 BOTANICAL GAZETTE [may 



Data taken as to position and number were arranged in the 

 form illustrated in table I, in which each leaf is classified with 

 respect to the position and number of its glands. For instance, 

 in Burbank 67 leaves bore two glands on the petiole and none on 

 the leaf in 1914, and in 191 7, 65 leaves fell in this class. A number 

 of other varieties could have been included, but these were selected 

 as typical of the great variability encountered. 



Table I shows that in number and position glands are extremely 

 variable on different leaves within a variety , but that the range 

 of variability is fairly typical for each variety. The number of 

 glands borne on the petiole is greater than the number borne on 

 the leaf base, and while the number borne in each position is 

 considerably different from season to season, yet the grouping 

 opposite each class is quite similar in each variety in spite of the 

 fact that the 191 7 data were taken from different trees, but of 

 the same clones, from those of 1914. Taking Burbank again as an 

 illustration of variability, it will be seen that some leaves have 

 no glands on either the petiole or leaf, while others bear as many 

 as five on the petiole and three on the leaf. If observations as to 

 gland condition made on a few leaves or herbarium specimens are 

 considered from the standpoint of the variation shown, it will be 

 evident that some caution must be exercised in classifying the 

 gland condition. 



Referring to the variability of glands within the species, it 

 will be seen that a similar condition is found to that shown within 

 varieties. A summary of the position and number of glands in 

 all the species investigated is presented in table II, in which the 

 gland condition is given for a total of 3477 leaves. 



Four points are of interest in table II: (i) without exception 

 there are more glands borne on the petiole than on the leaf base; 

 (2) when there is one gland present it may be borne either on the 

 leaf base or on the petiole; (3) when two glands are present, the 

 larger number is without exception borne on the petiole; and (4) 



than two glands are present, without exception a 



more 



strikin 



the 



with the 



