306 



DIFFERENT PARTS OF THE TUBERS OF 



DiOSCOREA ALATA SPROUT AT 



DIFFERENT RATES. 



In the Journal of the Asiatic Society of Bengal 1911, p. 467. I 

 gave an account of observations on the bulbils Dioscorea bulbifera, 

 Linn., showing that shoots are more freely formed from the basal 

 part of the bulbil than from the apical; and that if the bulbil be halved 

 the shoots are generally produced towards the base on either half 

 but, that sprouting is quickest on the lower halves. I here give some 

 observations made on the tubers of Dioscorea alata, which show that 

 in them the older parts more quickly sprout than the younger. The 

 result is as would be expected, but to demonstrate it was desirable, 

 in connection with observations in hand on the earliness or lateness 

 of various races under study; for when we have recognised that 

 sets cut from different parts of a tuber send out shoots relatively 

 quickly or relatively tardily according to the position from which 

 they have been taken, we are one step forward from the danger 

 of comparing the unequal in attempting the separating out of 

 precocious and late races. 



The observations have been made in this way. Taking all the 

 tubers reported on in the preceeding note pp. 297-302, they were cut 

 up into sets of about two pounds weight each, and planting was done 

 on December 2nd, 1914, in such way that the oldest part of each-tuber 

 was towards one end of the trenches dug for the crop, and the 

 youngest parts towards the other end. The sets, which had pre- 

 viously been treated carefully with potassium permanganate and 

 dried until the cut surfaces were hard, were earthed over to a depth 

 of about four inches and tnen the appearance of their shoots above 

 ground was watched for and recorded in the number of days which 

 on their emergence had elapsed from planting. The following table 

 details the result: in the first column is the number or name under 

 which the race has been grown, in the other columns are the number 

 of days between planting and the appearance of the shoots above 

 ground. The reader will s^e that a lesser period is generally recorded 

 in the second column than in the others and that the period lengthens 

 towards the right, i.e., towards the tip of the tuber.- As some of the 

 tubers were branched e.g., that figured, as No. 2 on page 299, the order 

 in which the parts were placed could not he made in every case to 

 represent exactly the actual tuber, but nevertheless the general result 

 is quite obvious, namely, that the more or less woody top of the 

 tuber is the most ready to sprout and the tip least. As man usually 

 keeps the top for propagation and eats the tip, which it the most 

 esculent, in so doing he gets the advantage for his planting of using 

 that part which nature has most ready for the purpose. 



There is evidence in the table that races vary considerably in 

 precocity or lateness, thus the latest named yam showed itself most 

 distinctly earlier in sprouting than the one inmiediately before it: 

 and the yams which w^ere figured on page 301 showed themselves 

 late; but these and other similar observations will be the subject of 

 another report, when more statistics are available. 



