1890.] The Distribution of Plants. 827 
with different combinations of characters, it will be seen how 
much geographical distribution may be made to check the value 
given to generic or other groups founded upon technical distinc- 
tions.” In other words, he inaugurated the actual use of facts of 
geographical distribution as an aid to classification." 
The method pursued by Gray and Hooker in determining the 
species that occupy a given region, and comparing this region 
botanically with others, brings the geographical side of the ques- 
tion into prominence ; and in the hands of botanists conversant 
with the principles of physical geography it has served to furnish 
important evidence bearing upon questions that are properly of a 
geological nature. Bentham’s method, on the other hand, 
consisting in the exhaustive study of various families of plants, 
with the distribution of each of their species, as far as this is 
known, the world over, suggests greater possibilities than the 
former, inasmuch as it offers at least the hope of one being able 
some time to follow, step by step, the descendants of a common 
ancestor as they have spread themselves over the face of the 
earth. Such monographs as those of Bentham’s on the Campan- 
ulacez ™ and Composite are excellent specimens of what has 
already been accomplished in this direction, and if they are 
somewhat disappointing in coupling few conclusions with enor- 
mous labor, they point out none the less the way in which those 
who care to lay solid foundations for future studies of this kind 
will probably choose to work. 
Thus far it has been attempted rather to indicate the successive 
steps that have been taken in this line of investigation since the 
time it became a subject of scientific inquiry, rather than to dis- 
cuss results and theories. If, now, a brief summary of the present 
status as a whole is made, it appears, in the first place, that the. 
observed facts relating to the distribution of plants correspond 
in every essential respect with what has been observed of the 
2 The results of Bentham's studies ‚up to 1869 are — in the presidential 
; of that year to the I n. des Sci. Nat., Sér. = 
Tom. XL), and are summarized by Prof. W. T. Dyer in the gua “ Distribution ;' 
the Encyclopedia Britannica. 
M Jour. Linn. Soc., Vol. XIII. 
15 Ibid., Vol. XV 
