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TRANSACTIONS OF THE SECTIONS. 73 
the action of each of these causes, so that it may be compared with that of the ordi- 
nary: action of the causes influencing the plant in its natural condition, if this process 
were repeated: upon the progeny of the original plants, and upon their offspring in 
continued succession, so as to imitate as far as we can the actual influences which take 
effect in nature, and the whole series of experiments were continued for a long period ; 
twenty, thirty, perhaps fifty years would scarce be sufficient; then, I think, those who 
shall succeed us, to whom we bequeathe the results, will be enabled far more safely 
than we can to establish a theory as to the nature of the relations of individual forms 
amongst plants. 
Even those who conceive the hypothesis of the descent of all the individuals of a 
species from a common original to be an essential point in natural history, cannot 
afford to dispense with such a course of inquiry ; for admitting the hypothesis, there is 
yet no practical test afforded by which to recognise the members of the species in 
groups where these are subject to great variation, nor can such a test be supplied in 
any other manner. Still more, those who believe it to be unphilosophical and in no 
way necessary to assume the truth of an hypothesis supported merely as the one in 
question is by @ priori considerations, whatever probability we may choose to assign 
to it, will desire that a body of facts bearing so directly on the question should here- 
after be forthcoming. 
It might also be desirable that a few members of the Section should associate for 
the purpose of collecting and arranging such well-established facts respecting the va- 
Fiations of plants as observed either in the natural state or in cultivation, as now lie 
scattered through botanical works, or may hereafter be supplied by observers, with a 
view to illustrating the value of specific characters in various groups. 
As to the modifications proposed in the forms of descriptive botany, it appears to 
ine that it should be an essential point in the character of a genus to assign, not merely 
the points of structure in which all the species of the genus agree, but also those which, 
varying from one species to another within the genus, yet remain constant throughout 
the subordinate varieties of these species, thus supplying what we call the specific 
characters within the group. An attempt of this kind, however imperfect, would at 
once ensure an accumulation of important facts, and by embodying these into our 
systematic arrangement, would prepare the way for important generalisations. An 
immediate result would be, that we should hereafter less frequently find one supposed 
species of a genus rejected because its characters had been proved to be variable, while 
another species of the same genus is admitted, though possessing exactly the same and 
no better distinctive characters. 
The other modification which I propose has a similar tendency with the last. It 
will not be considered improbable to assert as I do, from the study of several com- 
plicated groups, that in species of the same genus, the varieties of any single species, 
considered as diverging from a common typical form, recur in a similar cycle through- 
out all the species of that genus; and if, as is usual, we indicate varieties by letters of 
the alphabet, it seems natural to ask, that in describing a given group, the same letter 
should always indicate the same corresponding variety, each letter receiving from the 
first a fixed signification. I am inclined to go one step further than this. It is now 
admitted that there are two very distinct classes of varieties; the first, properly so 
called, represent the initial variations produced by modifying causes; they appear 
amongst the offspring of one parent plant, and usually return to the primary form as 
soon as the modifying action ceases, either in their own persons or in those of their 
descendants; the second, conveniently named sub-species, are permanent, and only 
after several successive generations do they return to the typical form, if indeed they 
_ be capable of so returning, which is scarcely yet established. Now, I assert, there is 
evidence to show that if we take the cycle of varieties displayed amongst the offspring 
of the original or typical plant, we shall find a cycle of sub-species, sometimes of course 
incomplete, exhibiting the same tendencies to variation of form in a more marked 
‘manner, while in each sub-species the same cycle of varieties is again repeated. Now 
if it be admitted that this law may hold good throughout, there will be no objection 
to designating the varieties each successively by a small letter, and each correspond- 
ing sub-species by a large letter of the same kind. It is needless to point out how a 
range of facts would thus be admitted into our systematic arrangements. 
errs 
Gassis 
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