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PETIOLAR GLANDS IN THE PLUM 1 



M. J. DORSEY AND FREEMAN WEISS 



(with PLATES XX, XXl) 



True functional glands are present in the plum in three posi- 

 tions: on the leaf serrations, on the leaf base, and on the petiole. 

 In the peach, plum, and cherry, the petiolar glands have been 

 given a place of considerable taxonomic importance. In the 

 course of the fruit breeding work at the Minnesota Agricultural 

 Experiment Station, excellent material became available for a 

 study of the glands in the plum in certain hybrids and pure forms. 

 Since certain questions regarding their variation and morphology 



appeared to be as yet open, the investigation reported herein was 

 begun. 



In a historical review of the taxonomic use of the petiolar 

 glands in the stone fruits, Gregory (3) showed that the earlier 

 writers had ignored these structures; while later pomologists had 

 made use of them in distinguishing major groups, as in the peach. 

 Other writers, however, questioned the taxonomic value of glands, 

 because of the variation observed in number, shape, and position. 

 From an extensive study of the leading varieties of the peach, 

 Gregory concluded that on typical shoots the glands were con- 

 stant, and that in many cases their shape could serve to separate 

 groups of varieties. He arranged the better known peach varieties 

 under three types of glands, reniform, globose, and indistinctive, 

 but pointed out that mixed and transitional types occur. 



Hedrick and others (4) record the gland condition on the 

 petiole and leaf serrations in the descriptions of the principal 

 varieties of plums in New York. Similar data have been brought 

 together for cherries (Hedrick et al. 5) and peaches (Hedrick 

 et al. 6). In the latter work the statement is made that "no one 

 familiar with any considerable number of varieties of peaches 



^ 1 Published with the approval of the Director as Paper no. 160 of the Journal 

 Series of the Minnesota Agricultural Experiment Station. The writers acknowledge 



tneir indebtedness to Dr. C. O. Rosendahl 

 Ernest Dorsey and James Gray for assistant 



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[Botanical Gazette, vol, 69 



