ENTOMOLOGIST AND BOTANIST. 



381 



miles arc not so iniich cut off. It is from tlie 

 west coast of iScotlaiul. I founcl it growing with 

 Asplenium marinum and A. adiantum nigrum, 

 on exposed rocks that were washed by the waves 

 of the Atlantic. 



From the above dcscriijtiou it would be diffi- 

 cult to define the exact habitat or range of tliis 

 rare little fern. 



THE ROCKY MOUNTAIN ALPINE REGION. 



1<Y C. O. PARBY, WASHINGTON, D C. 



(Selected.) 



The wooded belt of coniferous trees that, with 

 irregular local iuterniiitious, clothes the Rocky 

 Mountain slopes, conunences by a somewhat scat- 

 tering growth near their base, at an average eleva- 

 tion of six thousand feet above the sea. This belt 

 acquires its densest growth, and exhibits the great- 

 est number of distinct species, between seven 

 thousand and nine thousand feet elevation, and 

 terminates by an abrupt well-marked line at an 

 average height of eleven thousand three liundred 

 feet. 



These plainly recognized features are readily ex- 

 plained by reference to the corresponding climatic 

 conditions here exhibited. Thus the growth is most 

 dense and varied where the exposures present a 

 suitable condensing surface, and where there is 

 the greatest and most regular amount of aqueous 

 precipitation, caused by a mingling of the cool 

 descenduig currents of air from the higher elevations 

 meeting the warm ascending cm-rents charged with 

 moisture from the heated plains below; at this 

 irregular point of junction, summer rains and dews 

 are frequent, and the conditions for arborescent 

 growth are most favorable. At still higher eleva- 

 tions the actual limit of tree growth is determined 

 by conditions of temperature, which satisfactorily 

 explain the peculiar features of vegetation here mot 

 with. 



Most noticeable of these is the singular abrupt- 

 ness by which this limit of upright tree growth is 

 here marked. You are struggling through a tangled 

 maze of fallen timber and dense underlirush, over- 

 shadowed by tall trees with spreading roots bedded 

 in a saturated "pongy soil, when suddenly, without 

 any sensible dwarfing of intermediate forms, you 

 come upon open spaces, where stunted trees, fan- 

 tastically gnarled and twisted, with depressed flat- 

 tened summits, offer little obstruction to the open 

 view above. Through these obstructions, stepping 

 on the verj' tops of matted trees, which a few rods 

 below rear their pointed spires to a height of chirty 

 to forty feet, you come upon the bare alpine slopes, 

 which continue with variously interrupted rocky 

 exposures to the dividing ridge two thousand to 

 twenty-flve hundred feet higher. 



In the absence of any continuous meteorological 

 observations at or above the timber line, the most 



satisfactory explanation of the peculiar features 

 here presented is this: The so-called timber line 

 marks the extreme point o( iinnimum winter tempe- 

 rature, below which no exposed plienogamons vege- 

 tation can exist. All th.at survives above this point 

 does so by submitting to a winter burial of snow, 

 beneath which protecting cover it is enabled to 

 maintain its torpid existence. The early autumnal 

 fall of snow commences in the latter ])art of Se])tem- 

 ber, and receives constant additions through the 

 fall and winter months, during which it retains Its 

 light feathery texture, and is not sensibly wasted 

 by melting till the clear lengthening days of e.arly 

 summer dissolve them rapidly, giving origin to the 

 dashing streams that pour down the upper valleys. 



It is the pressure of this accumulating weight of 

 snow that gives the fantastic shape to the tree vege- 

 tation, that struggles for existence above the well 

 marked timber line, and we can readily note in- 

 stances, here and there, where from some peculiar 

 condition of wind, or a limited amount of winter 

 snow in particular seasons, points and patches of 

 dwarfed tree growth being left unjirotected, have 

 been blasted and destroyed. Otherwise we can 

 observe still more frequently where ambitious up- 

 per branches projecting into the sunlight of this 

 Arctic winter, have been nipped and killed. In 

 these unmistakable signs of the struggle for vegeta- 

 ble existence .are also exhibited some of the most 

 peculiar and marked features of tlie Alpine scenery. 

 This dwarfed tree growth, persisting above the 

 timber line, is as we might naturally suppose eon- 

 fined to sheltered valleys, or on the le.a-side of ab- 

 rupt rocks, where the drifted snow lies heaviest. 

 The point of greatest snow accumuhition is m.ainly 

 determined by the shelter afforded along the upper 

 line of the timber growth, at which locations the 

 snow drifting from the bare spaces above is lodged, 

 hence early in the thawing season these locations 

 offer the principal obstructions to travel, presenting 

 treacherous fields of snow, often overarching rush- 

 ing torrents; here also the vegetation is longest de- 

 layed, and is comparatively meagre. It is on the 

 more open exposures above that the alpine flora 

 offers its greatest variety and most attractive fea- 

 tures, and through a brief flowering period, ex- 

 tending from June to September, presents a succes- 

 sion of forms and colors, attractive to the eye of a 

 naturalist, and such as is nowhere else so compre- 

 hensively exhibited. As these .alpine plants owe 

 their existence to the protection afforded by winter 

 snow, they naturally include a number of species 

 that also flourish at lower elevations.. Thus in the 

 accompanying list of alpine plants, out of one hun- 

 dred and forty-two species. I note fifty-six as ex- 

 clusively confined to the alpine exposures. The 

 usu.al characters of alpine plants here, as elsewhere 

 exhibited, consist in a dwarfed habit of growtli, 

 late period of flowering an»l early seeding, the 

 forms being almost exclusively perenni.al. 



01 Plienogamons plants persisting to the highest 



