32 



THE FARMER'S MAGAZINE. 



In assuming that a plant can transmit its indi- 

 vidual as well as its specific character through its 

 seed to the plants which they produce, I do not 

 mean to imjily that the action of this cause may 

 not be modified or wholly counteracted by the ope- 

 ration of the numerous other causes acting during 

 the growth of plants, especially by the modifying 

 influence which the soil exerts in virtue of its 

 mechanical and chemical constitution. The con- 

 trary must indeed be the case ; for the individual 

 character is, in the first instance, as I stated in 

 reference to the flax plant, the result of the action 

 of such causes. Whatever be the cause or causes 

 which produce the specific character of a plant, 

 they appear to be so powerful as to predominate 

 over the action of soil, climate, &c. The individ- 

 ual character is the measure of the effect of those 

 causes in modifying the specific type. If we 

 consider with Rochleder that the homoecmorphism 

 of plants, like the isomorphism of minerals, is the 

 result of chemical constitution, — and the opinion 

 seems I'ational, — all modifications in chemical con- 

 stitution, whether they consist in the production of 

 an abnormal substance, or in the development of 

 an abnormal quantity of one or more otherwise 

 normal constituents, must, if they at all affect the 

 seed, tend to perpetuate themselves — that is, to 

 l)roduce varieties. But nothing has yet been 

 done, strictly speaking, to trace the kind of modi- 

 fication in chemical composition which most affects 

 the germ. 



In plants which produce but one flower-stalk, 

 the whole of the germs are more likely to have the 

 same chemical composition, and therefore the same 

 structure, than where numerous flower-stalks are 

 formed on different parts of the same plant. As 

 each flower may be developed at different periods, 

 the chemical constitution of the sap may vary very 

 mucli within the intervals of time between the 

 formation of the several germs, and consequently 

 a different character may be impressed upon the 

 germs of each flower. But even the seeds con- 

 tained in the same capsule or pod often vary 

 considerably in size and density. This is well 

 seen in the leguminous seeJs, but it may be often 

 observed even in the case of such small seeds as 

 those of the poppy. In timber frees, and general- 

 ly in plants of slow growth, the constitution of the 

 sap appears to be more constant and less liable 

 especially to rapid modifications, or, at least, to 

 those which afiect the quality of the seed, than 

 herbaceous plants. This is, perhaps, due in some 

 measure to the various substances stored-up in the 

 vessels and cells, the j)roduce of former growth, 

 which serve to dilute or counteract the modifi- 

 cation. On this account, it is much to be regretted 

 that no one has determined whether the sap of the 



sugar-maple presents as great a variation in com- 

 position as the quick-growing sugar-cane and 

 beet-root. 



Plants being composed of chemical molecules 

 subjected to the action of the force or forces which 

 produce the phenomenon of life, a species may be 

 considered as simply a series of groups of such 

 molecules, whose motions fulfil, under a certain 

 relation of forces, the condition of the most stable 

 equilibrium. So long as the relation of forces 

 deviates very little from that which results in 

 equilibrium, the type is constant, and any devia- 

 tions from it are transitory. If the deviation be 

 considerable, we may have: — 1. A modification of 

 the type, which may be individual if the deviation 

 be transitory, or may result in the production of a 

 variety if constant; or 2. The deviation taking 

 place slowly and by successive ste[)s, so as not to 

 remove, for a moment, the molecules from the in- 

 fluence of the vital forces, a new condition of 

 equilibrium may arise, which would result in the 

 development of a new species ; or 3. The equi- 

 librium may be so disturbed as to remove, for a 

 moment, some of the molecules from without the 

 sphere of vital force, the immediate result of which 

 would be the deatli of the individual. If the 

 transmutation of species be possible, the chances 

 of the production of a new one may be set down 

 at not less than one in several millions at least; 

 while the conditions of equilibrium must impose a 

 limit to the possible number of species which can 

 exist under any given combination of physical 

 conditions, and the most stable arrangements 

 would naturally be those first attained. Now, 

 from this point of view, the question of the extent 

 to which a species might be permanently modified 

 has not yet, so far as I am aware, been examined. 



Although the action of chemical agents upon 

 plants has engaged the attention of many dis- 

 tinguished experimenters, yet beyond the great 

 outline sketched by Leibig, very few positive data 

 have been, up to this, acquired. Perhajis the cir- 

 cumstance, that hitherto the influence of chemical 

 agents has been only studied upon the individuals 

 of a generation, may in part account for this. 



Carefully conducted experiments should there- 

 fore be made, to determine the action of chemical 

 substances upon plants through the several suc- 

 cessive generations obtained from a single parent 

 plant. The seed of each plant, beginning with 

 that of the parent plant itself, should be carefully 

 distributed into several sorts, accoiding — 1. To 

 relative volume and density; 2. Shape, in reference 

 to normal type; 3. Position of the flower on the 

 plant, esj)ecially with reference to the action of so- 

 lar rays; 4. Period at which the flower of each 

 seed (if bingle) or of each pod, &c., was developed ; 

 and so on. In this way, whatever slight influences 

 might be exerted on the different seeds of the 

 parent plant, might be gradually exalted after two 

 or three generations. Such experiments should 

 not be confined to one or two fixmilics of plants, 

 because, no doubt, every family would be affected 

 more or less differently by the action of the same 

 causes. 



