116 EXCURSIONS IN MADEIRA 



that continent. It is an elegant plant, and would answer much 

 better than the arum, as all cattle will eat the herbaceous j^art. It 

 is remarked by Baron de Humboldt (Essai Politique, &c. p. 407), 

 that he did not find the d. saliva of Linneeus in South America, 

 and that it has not as yet been met with in the islands of the South 

 Sea ; and he adds, that the leaves of yams differ so much from 

 cultivation, that doubts may be entertained of the numlier of 

 species contained in this genus : it appears to me, however, that 

 the d. saliva is very distinct ; as it not only differs in leaf, but also 

 in its stem, which is small, deUcate, and cyhndrical, without a 

 trace of the lobes of the d. alata. The chestnut (fagus castaneaj 

 has proved a very valuable introduction ; it forms the principal 

 part of the timber of the island, and of the winter food of the 

 peasantry. The sici/os parvijlora, cited by Persoon, as indigenous 

 to Surinam, and called the tchu-tchu, yields abundantly, and would 

 be a very valuable addition to the vegetables of the tropical parts 

 of the Old World, as well as to Europe. 



I found the woad (isalis tinclorea), at Praya Formosa and at 

 Campanario. The ruivinho, generally found in the heights, is 

 certainly the true madder, although I could not see it in flower. 

 The stalk is that of the rubia linctorum ; its leaves are rough at 

 the edges only, whereas those of the variety sylvestris are rough on 

 both sides, and are in whorls of four and two leaves, instead of six 

 or seven ; neither are they linear and rough above, as in the 

 species angmlifolia. I am thus particular, because they are culti- 

 vating the wrong species near Lisbon, and are not aware that the 

 true one is indigenous to jNIadeira. The roots of the madder 

 should be allowed to swell in the ground for three years, and then 

 they wiU produce nearly 400 pounds to an acre, but it exhausts 

 the soil more than any other plant, except the indigo ^ The 



■^ The indigo thrives well in the gardens, and seems to be free from its destructive 

 insect. 



