THE BEHAVIOR OF THE NECTAR GLAND IN THE 

 CACTI, WITH A NOTE ON THE DEVELOPMENT 

 OF THE TRICHOMES AND AREOLAR CORK 



FRANCIS E. LLOYD and CHARLES S. RIDGWAY 



Alabama Polytechnic Institute, Auburn, Ala. 



The occurrence of extra floral glands in the Cactaceae has long 

 been known 1 and these structures have been used as taxonomic 

 characters. Ganong, in 1894, indicated their occurrence in a 

 variety of species of the genus Opuntia, and examined them from 

 the morphological-physiological point of view, describing in detail 

 their structure and mode of secretion in Opuntia arborescens. He 

 pointed out, also, that, at the time of his publication, they were 

 known in Mamillaria, Rhipsalis and Cereus. This list was ex- 

 tended in 1908 2 to include Echinocactus, of which several species 

 were found to have nectar glands on the mamillae. Other genera 

 might have been included but for the lack of suitable identifica- 

 tions. 



The purpose of this paper, however, is to rediscuss the structure 

 and the mode of secretion, as indicated by certain cytolytic changes, 

 of the cactus extrafloral nectar gland, which according to Ganong, 

 may be homologized with the thorn, a conclusion fully supported 

 by the evidence. After describing their development, Ganong 

 says of the histology of the gland: "die Zellen bleiben noch unver- 

 holzt und inhaltsreich, und eine Cuticula sondert sich ab, zwischen 

 welcher und der Drusenoberflache der Honig ausgeschieden wird. 

 Schliesslich zerreisst die Cuticula und der Honig steht als grosser 



1 Pertinent references are given by Ganong, W. F., Beitrage zur Kenntnisse der 

 Morphologie und Physiologie der Cacteen. Flora, Erganzungsbd, 1-40, 1894. 



2 Lloyd, F. E., Extra-floral nectaries in the cacti. Plant World, 11:138-140, 

 June 1908. The senior author regrets that, at the time of writing this paper, he 

 was in ignorance of Ganong's work on the nectar gland and neglected, therefore, 

 to cite it. 



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THE PLANT WORLD, VOL. 15, NO. 7, JULY, 1912 



