178 Propagatioyi of the Dahlia. 



practised by amateurs or others, anxious to obtain fine perfect 

 flowers for exhibition or otherwise. I speak advisedly, and 

 from experience, when I assert, that plants raised from cuttings 

 do not produce equally perfect flowers, in regard to size, form, 

 and fulness, with those produced by plants grown from divi- 

 sion of the tubers, the old method of propagating the dahlia. 

 It has been said that plants raised from cuttings flower more 

 abundantly than those raised by division ; but to this 1 am not 

 prepared to subscribe. 



Physiological botany readily accounts for the different results 

 of the two methods. The starch, or feculent matter, stored in 

 the roots, is intended by nature for the nutrition of the animal 

 shoots ; not only, until the tubers have formed, at the com- 

 mencement of the vegetating season, the spongioles necessary 

 for the absorption of the required quantity of pabula ; but also 

 when that the spongioles are unable, from drought, or other 

 causes, to absorb a sufficiency of nutrient matter, to sustain the 

 rapidly developing and vigorous vegetation. 



Plants propagated by cuttings cannot, of course, absorb the 

 nutriment prepared and stored, during the last season, in the 

 tubers of the mother root; and are forced to form spongioles 

 and tubers for themselves. But the fecula contained in these 

 latter is not, till towards the end of the year, suflScient in quan- 

 titj', or sufficiently ripened by the deposition of carbon, to be, 

 perhaps, in any way serviceable. 



The potato might be propagated by cuttings of the young 

 shoots, in the same way with the dahlia ; but such plants would 

 not, in the early stages of their growth, be nourished by the 

 starch of the tubers ; and, therefore, would neither be so strong 

 and vigorous as plants raised in the usual method, nor would 

 they yield a return equal in weight or quantity. 



It is well known that tubers and bulbs, when placed in damp 

 situations (the potato, for instance, in a damp cellar), develope 

 their leaf-buds; and that these continue to grow and elongate, 

 without the assistance of rootlets or spongioles, so long as there 

 is any fecula in the tuber or bulb; but that when this is ex- 

 hausted the stem withers and dies. We hence perceive how 

 important the nourishment derived from this substance is to 

 the vigour of the plant, and why whole tubers of potatoes pro- 

 duce larger crops than are produced by cut sets. Hence, too, 

 we may learn why perfectly ripe sets are so much move certain 

 of success than unripe ones ; the fecula in the former being so 

 much the more abundant, and more perfectly elaborated. To 

 the unripeness of the sets is attributable the failure of the po- 

 tato crops in some parts of Scotland, in the autumns of 1835 

 and 1836, and the consequent misery and starvation of the un- 

 fortunate peasantry. 



