DIOSCOREACEAE 



147 



in the Philip. Agr. and Forester 3 (1915) 207, plate 2, figs. 12, 

 U, 18. 



In a recent letter to me Mr. Burkill states : 



Of the Philippine Dioscorea alata I have in Singapore in a few races the 

 tuberous roots do not respond to geotropism in the normal way, but ascend 

 to the surface of the soil where conditions are apt to kill them. If 

 one continues to protect them by covering them with earth they continue 

 to grow and may become greatly elongated. The drawings of the yams 

 on page 30 of Gardens' Bulletin were made at a time when I had not 

 discovered how to earth them up. If you will examine the figure of 

 Rumphius's Ubium anguinum you will note that what I take to be the same 

 race is represented. I believe that this type of yam arose and was propa- 

 gated by planting it in the midden at the back door and that the yams 

 continued to grow upward with the accumulation of rubbish. 



Mr. Burkill calls my attention to the fact that Inhame St. 

 Thome of Piso is Dioscorea alata Linn., and that Rumphius was 

 wrong in ascribing it to his Ubium pomiferum. 



DIOSCOREA ESCU LENTA (Lour.) Burkill in Gard. Bull. Straits Settl. 1 

 (1917) 396. 



Oncus esculentus Lour. Fl. Cochinch. (1790) 194. 



Dioscorea combilium Ham. in Wall. Cat. (1832) no. 5103 A. 



Dioscorea fasciculata Roxb. Hort. Beng. (1814) 72, nomen nudum, 



Fl. Ind. ed. 2, 2 (1832) 801. 

 Dioscorea tiliae folia Kunth Enum. 5 (1840) 401. 

 Combilium Rumph. Herb. Amb. 5: 357, t. 126. 



This species is not represented in our Amboina collections. 

 The figure, however, unmistakably represents the form commonly 

 named Dioscorea tiliaefolia Kunth, but for which Prain and 

 Burkill have recently adopted the name Dioscorea aculeata Linn. 

 Sir David Prain, however, has discovered that Dioscorea aculeata 

 Linn, is the valid name for D. wallichii Hook. f. and that Oncus 

 esculentus Lour, supplies the oldest valid name for the species 

 under discussion. Linnaeus originally reduced Combilium to 

 Dioscorea aculeata Linn., in Stickman Herb. Amb. (1754) 23, 

 Amoen. Acad. 4 (1759) 131, Syst. ed. 10 (1759) 1293. Mr. 

 Burkill, who has called my attention to the necessary change in 

 the specific name of this species, considers that Combilium is 

 referable here with the possible exception of Combilium rubrum, 

 the status of which is uncertain, and C. tsjampadaha, which is 

 described as if a different species. 



DIOSCOREA PENTAPHYLLA Linn. Sp. PI. (1753) 1032. 



Ubium quinquefolium Rumph. Herb. Amb. 5: 359, t. 127. 



This species is not represented in our Amboina collections. 

 The figure probably represents the var. malaica Prain & Burkill, 



