by the Use of Charcoal. 153 



holes in the bottom of the pots into this under stratum. Among 

 other plants, this was strikingly the case with peireskias, casua- 

 rinas, and Thunbergz« alata; all of which, without any artificial 

 fecundation, ripened a quantity of seed, &c. M. Lucas very 

 properly thought it necessary to follow up this chance discovery 

 in a number of experiments, by adding a proportion of charcoal 

 powder to the usual mixed soil in which plants were already 

 rooted, and also by using it pure for cuttings instead of sand. 



About the middle of July he communicated to me the result 

 of his experiments, and I thought the importance of the case 

 required that I should urge him to make greater and more 

 varied observations. Accordingly, plants from many different 

 families were chosen, cuttings made from twigs, leaves, parts of 

 leaves, &c., and a day-book kept of the results. The time is 

 too short to allow of a perfect account of all that took place to 

 be given ; and circumstances did not allow of all due attention 

 being paid to the experiments at that busy time of the year. 

 Yet I think that the results already attained give sufficient proof 

 of the advantages of this method. When cut leaves of the 

 mimosas and zamias, encephalartos, and agave, and leaf-bundles of 

 Pinus excelsa, &c., form a callus in a short time, from which 

 they put forth strong roots ; when cuttings of other plants root 

 and grow in a much shorter time, and more certainly, than by 

 any other method; I think it high time to lay the case open to 

 the approval of competent judges. I shall refrain from saying 

 anything of the cause of charcoal's stimulating the growth. 



With respect to increasing plants by leaves and parts of 

 leaves, I must mention that those leaves are most suitable for 

 the purpose that have strong prominent veins. In parts of 

 leaves, for example, the callosities are always formed at the cut 

 ends of the veins, so that, according to the position and direction 

 of the latter, a leaf will form a callosity at the same time from 

 the central vein, and from the second, fourth, &c., side veins. 

 These callosities often attain the size of a large pea before put- 

 ting out roots, and form a bud which continues to £;row as a 

 separate plant. It is of advantage in many cases, as soon as the 

 growth of the callosity is sufficiently advanced, to remove the 

 cutting from the charcoal into a proper sort of mould ; and, by 

 this means, the little knob being able to provide its own nourish- 

 ment will prevent the untimely exhaustion of the parent leaf. 

 If this precaution is delayed, an entire stoppage takes place in 

 the growth ; the knob produces neither roots nor buds, and dies ; 

 because the parent leaf cannot yield any more nourishment, and 

 the charcoal appears to have a preserving and stimulating rather 

 than a nourishing quality. 



I leave it now to M. Lucas himself to give the experiments 

 hitherto made. 



