66 



MEMORANDA CONCERNING THE MELLOCA. 



" A little later in the season, and when the external atmos- 

 phere was damp, the stems presented another rather curious 

 phenomenon ; their extremities, which, a few days before, had 

 very short internodes, and leaves in whorls, suddenly lengthened, 

 and, becoming more slender, were at last transformed into a 

 thread, bearing at long intervals small, nearly scale-shaped 

 leaves : these threads, after running along the ground or over 

 the neighbouring branches, with a manifest preference for dark 

 places, entered the earth, where their extremities became tubers. 

 They are, I am certain, direct prolongations of the stems, and 

 not, so far as I could discover, axillary productions from the 

 leaves at their extremities. This lengthening of the stem into a 

 thread appears to me to be connected with moisture and a low 

 temperature. It took place, in those plants which I had put in 

 a cold pit, in the spring ; but, being less general, it had not 

 struck me so forcibly as it did in the autumn, when it took place 

 on all the plants. In the spring plants, the first threads which 

 were developed entered the earth and formed tubers, whilst those 

 which appeared later, or which met any obstacle, again, under 

 the influence of a higher temperature, gave birth to leaves regu- 

 larly arranged ; the internodes shortened, the stem assumed its 

 natural size, and at the same time sought the light I thus wit- 

 nessed the curious phenomenon of stems undergoing two succes- 

 sive contractions and thickenings. This is certainly very inter- 

 esting, and well deserves the attention of physiologists. 



" We are not yet able to judge of the nutritive qualities of the 

 Melloca. The tubers that came from Peru were not very 

 pleasant to the taste ; they were flabby, semi-transparent, and 

 evidently exhausted by the numerous shoots that had grown during 

 the voyage. 



" The young tubers collected in 1848 were too young to give 

 more than a very imperfect idea of the value the plant is likely 

 to acquire as an article of food. Their taste was tolerably plea- 

 sant ; but (in consequence, probably, of their not being ripe) 

 they were very watery. With the aid of a microscope I found 

 that there was an abundance of starch in the cortical or outer 

 zones of the young tubers, but less (and that finer) in their inte- 

 rior or medullary portion ; the thickness of these two zones, 

 measured from the circumference to the centre, is pretty nearly 

 equal. The grains of starch are roundish, very smooth, rather 

 lar<£e, and not unlike those of Oxalis crenata or Oca. M. Maason 

 recommends the leaves as Spinach. 1 must say that, for my 

 own part, I did not like it ; but I ought to add, perhaps, that 

 Basella, and, in general, all those plants which become viscid 

 when cooked, are not to my taste. M. Masson succeeded much 

 better than I in cultivating the Melloca : his plants were in 



