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appear to be frequent only in the north. It is indeed properly a 

 plant of high and even arctic latitudes, but of great climatic adapta- 

 tion, and admirably exemplifies that axiom of botanical geography, 

 that the polar* limits of plants are far more abrupt and definite than 

 their equatorial boundaries; in other words, that species proceeding 

 from the equator towards either pole, have their vanishing-points 

 more distinctly traced on the earth's surface than those descending 

 from higher to lower latitudes; and the reason is obvious: cold is so 

 uncongenial to vegetable life, and warmth so propitious, that a small 

 increase of the former, or what is the same thing, diminution of the lat- 

 ter, suffices to arrest the development of a species whose constitutional 

 tendency is to warm or temperate zones of habitation, but a moderate 

 excess of heat beyond what is requisite for healthy and vigorous ve- 

 getation, seems to affect the majority of plants but little, as we see in 

 so many alpine species, which thrive in our low and warm gardens 

 as well as on their native mountains. Besides, the plants of cold cli- 

 mates, in their advance towards warmer regions, can and do take 

 shelter from an undue temperature in lofty, humid, or umbrageous 

 places, but the deficiency of heat is very partially and imperfectly 

 supplied to plants migrating from warmer to colder latitudes by shel- 

 ter and radiation, conditions which can only be found in a few fa- 

 voured spots. Of this species of willow-herb, two very tolerably 

 constant and well-marked forms occur with us in Hants. The first of 

 these is distinguished by its usually smaller size, narrower leaves, 

 which are of a darker green, and much waved or wrinkled, and consi- 

 derably glaucous beneath, as also by the narrower or more contracted 

 spike of smaller and deeper-coloured flowers. The second variety 

 resembles the garden state of the plant, in its flatter and broader 

 leaves, of a brighter green, and scarcely, if at all, crisped or wrinkled, 

 in its larger and paler flowers and more expanded spike, the entire 

 plant very handsome and stately. The capsules I find similar in 

 both forms, that is, erect and much elongated, nor have I met with 

 any wild plants in which the seed-vessels were short and spreading, 

 as we find them in cultivation (E. brachycarpum, Steph.), a state aris- 

 ing, I suspect, from arrested development consequent on the increased 

 disposition, in a plant already prone to that mode of multiplication, 

 to propagate by the root, which the rich and loose soil of a garden 



* I use the terms polar and equatorial as alike applicable to both hemispheres of 

 our globe, whilst those of northern and southern, being of opposite attributes on each 

 side of " earth's central line," of course are not convertible. 



Vol. hi. 3 b 



