BENTHAM ON THE SPECIES AND GENERA OF PLANTS. 137 



found to break out occasionally into a return to the typical form, or to 

 be connected with it by numerous intermediates. Generally speaking, 

 such of these aberrant races as have sj)read to the limits of the geo- 

 graphical area of the species, or have become introduced into distant 

 countries, and have thus been adapted to a change of condition, will 

 there be found more disposed to maintain their peculiarities, or even to 

 diverge still more from their types. It is where the species is most at 

 home, where it accommodates itself most readily to a variety of soils and 

 exposures, where the stations it affects show a most ancient domicile, 

 that the connecting links between the varieties it has produced must 

 generally be sought for. And this is one great reason why permanence of 

 form is so little conclusive as evidence of specific difference, unless ob- 

 served in a considerable portion of the area of the species. 



The investigation of the connecting links between two forms, with 

 the view of determining whether they are distinct species or marked 

 races of one species, is attended with great difficulty in the due appre- 

 ciation of what are intermediates — of the difference between one or two 

 definitely limited, though apparently intermediate species, and a chain 

 of intermediate forms connecting the two extreme varieties of one spe- 

 cies. The Allsike clover, in the colour of its flowers and mode of 

 growth, has been looked upon as intermediate between the Dutch and the 

 common red clover (T. repens andprateme), and some such idea sug- 

 gested to Linnaeus the name of T. hybriclum. Yet the evidences of its 

 specific distinctness from both are very strong. I have observed it with 

 care in a living state over a great part of its natural area in Sweden 

 and Central Europe. From T. pratense it is separated by characters 

 among the most constant in the genus, without, in this instance, any 

 tendency to variation. It is nearer to T. repens; and Professor Buck- 

 man, at the meeting of the British Association at Cheltenham, in 1856, 

 stated that he had found it degenerate into that species. I cannot 

 but think, however, that here there must have occurred one of those 

 mistakes so common in botanical and experimental gardens — that a plant 

 or its seeds have accidentally perished, and its place has been taken by some 

 ubiquitous species, so nearly allied as to escape observation when young, 

 such as, in this instance, T. repens. I never could detect, either in those 

 places where I have seen T. hyhridwm wild in the greatest abundance, 

 nor yet in the fields where it is cultivated, any tendency to assume the 

 creeping stems, the peculiar inflorescence, and other characters of T. 

 repens. 



Take, again, Hypericum linariifolium. The cursory inspection of 

 a few herbarium specimens of this plant, of certain varieties of H. 

 perforatum, and of H. humifusum, might suggest the idea that the 

 former constituted a connecting link between the two latter. In this 

 instance the characters are less decided, and of a less constant nature 

 than in that of the three Clovers above quoted ; yet, so far as my expe- 

 rience goes — and I have observed H. linariifolmm living in parts of 

 "Western France, where it grows in the greatest abundance, besides nu- 

 merous dried specimens from the greater portion of its area, and the two 



VOL. I. — N. H.E. T 



