VOLUME XXXIV 



NUMBER 6 



Botanical Gazette 



DECEMBER. igo2 



A MORPHOLOGICAL STUDY OF CERTAIN 



ASCLEPIADACEAE. 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY. 



XLI. 



Theodore C. Frye. I1\ 



(with PLATES XIII-XV) 



In a previous paper (7) the results of a study of the pollen 

 of certain Asclepiadaceae were published, and during that investi- 

 gation the remarkable structure of some of the floral organs 

 attracted attention, Thepresent paper is the result of their study. 



The species studied were Asclepias Cornuti Dec, A. Stdlivantii 

 Engelm., A. nibra L., A. phytolaccoides Pursh, A. tuberosa L., A, 

 incarnata h.^ A. obtusifolia M i c h x. , A. verticillata L. , Acerates 

 longifolia Ell., and A. viridtflora Eaton. The material was all 

 collected in the vicinity of Chicago, and in the field plunged into 

 weak chromo-acetic acid. The safranin, gentian-violet, orange 

 combination proved to be the best stain for critical work, 

 although it was often better to omit the orange. The stages 

 were most completely followed in A. Cormiti, and the following 

 account applies to it unless otherwise stated. The chief diffi- 

 culty lies in the small size of the embryo sac. A, Sullivantii 

 is a better form, since it has a larger flower, but it was not found 

 in time for young stages. The other species were examined for 

 comparison, and show essential similarity; but any important 

 disaa^reement is noted. 



The family has received considerable attention, but aside 



389 



4P 



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