A STUDY OF THE HISTOLOGY OF THE STEM OF THE 

 WAX PLANT, HOYA CARNOSA (L.) R. Br. 



By John I. Northrop 



In the fall of the year 1886 Dr. N. L. Britton suggested that I 

 study the anatomy of the wax plant, Hoya carnosa, as it appeared 

 to be hitherto undescribed and possessed interesting peculiarities of 

 structure. 



From that time to the present I have had the investigation in 

 hand and the following pages present the result. 



History 



I have been unable to find any account of the discovery of the 

 wax plant or mention of the name of the person who first collected it. 

 Linnaeus named it Asclepias carnosa; and Loureiro, under the name 

 of Stapelia Chinensis, describes a plant which he thinks may be the 

 same as that called Asclepias carnosa by Linnaeus. 



In 1809 Robert Brown divided the order Apocinece, retaining the 

 old name for one part and calling the other the Asclepiadece. In the 

 latter order he named for Thomas Hoy, an '* intelligent and success- 

 ful cultivator," for some time gardener to the Duke of Northumber- 

 land, the genus Hoya, in which he placed the Asclepias carnosa of 

 Linnaeus and the Stapelia Chinensis of Loureiro, uniting them under 

 the name the plant has since borne, Hoya carnosa (L.), R. Br. 



Brown considered the wax plant the type of the genus, and states 

 that it "probably includes several species which can only be determined 

 from living specimens." As its habitat he gives tropical Asia and 

 New Holland. 



De Candolle, in his " Prodromus," gives for localities "Eastern 

 India, tropical Asia, around Canton" (quoting Loureiro), and ques- 

 tions New Holland. George Bentham, in the "Flora Hongkongensis," 

 for localities gives "Mount Victoria, Champion; also in adjoining 

 continent, not known for certain out of South China, but probably 



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