MEMORANDA CONCERNING THE MELLOCA. 



65 



very incomplete, and related almost entirely to the preserva- 

 tion of the tubers, ' which cannot be effected for more than three 

 or four months in a dry, fresh place. If the tubers are kept 

 longer than that, the eyes begin to develope ; their growth does 

 not, however, affect the tuber's power of germination. When 

 spring — the time at which the tubers ought to be planted — is 

 arrived, the shoots are taken off, and they themselves serve very 

 well for propagation. So long as the tuber is not completely 

 dried, it remains fit for planting. After the shoots are removed, 

 the tubers are left in the sun for a few hours to dry.' The tubers 

 received by me were in a very advanced stage of vegetation — 

 withered and exhausted. Some were immediately planted in a 

 frame — an unnecessary precaution ; and at the beginning of 

 May I had 40 good plants. The Melloca is half a runner ; 

 its shoots, without support, send out roots wherever the ground 

 is touched ; its leaves are thick and fleshy ; from being large 

 and spreading, they become erect and round like a shell in 

 the fully developed plant. The flowers, which are small and 

 greenish, spring in spikes from the axil of the leaves. The 

 produce of the Melloca consists in its tubers, which, in their 

 native country, attain a considerable size. They are yellow, 

 very smooth, full of starch, and appear on runners proceeding 

 from the base of the stem, and tending to rise to the surface of 

 the soil ; the plant must, therefore, be pretty well earthed up. 

 In general my tubers did not begin to grow till the autumn rains 

 had begun, so that they were still very small when the frosts set 

 in. Some plants, however, under sashes produced tubers in 

 April ; but when planted out in May, although great care was 

 taken not to disturb them, they did not continue to increase in 

 size; they behaved like sets, shrinking and sending out new 

 shoots. During the three summer months, vegetation was de- 

 cidedly checked ; this is to be attributed rather to heat* than to 

 want of moisture. The plants, which were at this time well 

 watered, produced plenty of leaves, but no tubers. The return 

 of a lower temperature was remarkable, on the contrary, for the 

 rapid development of adventitious buds on the tubers ; and this 

 effect was, I think, much more quickly perceptible on those 

 plants which had suffered from drought than on the more 

 vigorous ones which had been watered. 



* From the middle of the summer I had foreseen this result, in conse- 

 quence of some valuable information given me by M. Boussingault respect- 

 ing the atmosphere and temperature of the table-lands of the Andes. He 

 advised me, at this time, when I attributed the abortion of the flowers to the 

 coldness of our summers, not to raise the temperature of the medium in 

 which my plants were, as I had intended doing, and it will be seen in the 

 sequel that this advice was well founded. 



VOL. V. F 



