For October. 1921 



725 



Vegetation and the Cold 



WILLARD N. CLUTE 



THE contention of ihe "oldest inhabitant" that the 

 Winters are not as cold as they used to be is un- 

 doubtedly correct, though it is not likely that he 

 knows any more about it than the rest of us. There is 

 ver\- positive evidence that the temperature of our globe 

 has been much lower than that experienced by any living 

 man. but the changes that take place in climate are so 

 slow and so gradual that they cannot be perceived in a 

 single lifetime, or in many lifetimes, for that matter. 

 It seems certain, however, that this old earth has been 

 frozen up and thawed out, not once but many times, and 

 it has been dried up and moistened and dried up again. 



It is not very far back to the last period of refrigera- 

 tion as geologic time is measured. A matter of thirty 

 thousand years or so would take us to a period when 

 the most populous part of Xorth America was buried 

 beneath a great ice-sheet a mile or more in thickness. 

 The southern edge of this stupendous glacier reached in 

 some j>laces to the Ohio A'alley while its western border 

 was in the vicinity of the Missouri river. There were 

 also other accumulations of ice in the Rockies and along 

 the Pacific Coast. 



The long period of cold that preceded the last glacial 

 period naturallv killed all plants over a vast area and 

 the ice that followed blotted out the evidence of their 

 former existence with a thick sheet of sand, clay and 

 gravel derived from the rock refuse ground up as it 

 slowly moved over the land. It is evident that the onset 

 of the cold was -gradual for though the plants were killed, 

 vegetation as a whole had time to migrate southward 

 before the advancing ice. We still find stranded on moun- 

 tain tops, far from the Pole, remnants of that Arctic flora 

 which pushed forward in those troublous times and for 

 some reason failed to return when the seasons were more 

 proi>itious. One can imagine a long series of years each 

 colder than the last until the ice of one Winter merged 

 with tliat of the Winter following thus laying the founda- 

 tion for the vast accumulations of ice that were to follow. 



When a milder period dawned, the ice probably dis- 

 ap])eared as slowly as it came. It has not yet entirely 

 given up the struggle and still persists in the interior of 

 (ireenland. Nor was its banishment from our own region 

 accomj/iished without many a stubborn battle between 

 the forces of the sunshine and the frost during which 

 the battle ground was over-run again and again. In 

 Illinois there are indications of no less than seven separate 

 invasions of the region by the ice. Whenever the ice 

 melted, plant life pushed into the area uncovered and the 

 birds followed. Many people see in these migrations back 

 and forth, the origin of l)ird migrations in general. It 

 is not possible for man to predict with certainty another 

 glacial i)eriod, but we know that there has been more 

 than one and that at the ])resent time we appear to be 

 living in a warmer jicriod between what will prove to be 

 successive glaciations. 



15efore the last glacial period, the climate was much 

 warmer than it is at present, for palms and tree ferns, 

 as well as manv plants of temperate regions, grew as far 

 north as (ireenland. .Spitzbergen and Xova Zcmbla. In 

 fact. ])lants were so abundant in those regions as to form 

 seams of coal thick enough for ])ri)fitable mining. The 

 area is now occupied by vegetation of a very dit^erent 

 character whose origin the scientist is often puzzled to 

 account for. It is commonly assumed that the plants 

 of the present originated various devices to protect them- 



selves from the cold and thus equipped pushed into the 

 borders of the glaciated region and slowly penetrated to 

 their present homes. A similar origin of desert plants is 

 usually accepted. .AH such are supposed to have evolved 

 means for surviving great drouth and thus have been 

 able to penetrate to the most arid regions. 



The criticism that may be brought against such theories 

 of the origin of the protective structures of plants, is that 

 they are supposed to have appeared in the jilants before 

 they were useful to them. It is quite apparent, however, 

 that this would not likely be the case. A much simpler 

 explanation, and undoubtedly the correct one. is easy to 

 find and the phenomena of the glacial period give plausi- 

 bility to it. \\'hen the cold of the glacial period l>egan to 

 be noticeable, the palms and ferns would succumb at once, 

 but the hardier plants of the temperate regions, being less 

 susceptible, would linger on and only give up the fight 

 after long struggle. Time after time the tender shoots 

 must have been killed or the whole plant cut down to the 

 ground, until they were taught to turn their tips into buds 

 and their leaves into bud-scales. Those killed to the 

 ground developed the underground or geophilous habit 

 which is now illustrated by a multitude of bidbs. tubers, 

 corms, and rhizomes. Many species undoubtedly perished 

 before they could acquire a protective covering, but the 

 successful ones, of course, continued to reproduce their 

 kind, steadily becoming better adapted to the conditions. 

 In a similar way, desert plants appear to have adapted 

 themselves to drouth conditions. I'hose that failed to do 

 so perished when the region became too dry. If the 

 change be only gradual enough, it is likely that the ma- 

 jority of plants can adjust themselves to greatly changed 

 conditions. The desert made the cactus plant ; in the 

 Old \\'orld where there are no cacti, other plants have 

 taken on their characteristic forms in response to similar 

 conditions. .Annual plants are plentiful in both Arctic 

 and desert regions. Here we have a very different re- 

 action to inhospitable conditions. Dying has become an 

 adaptation for avoiding; both cold and drouth, but before 

 dying, the plants leave behind peculiarly resistent parts 

 of themselves (which we call seeds) that .spring up in a 

 milder season to reproduce their race. 



A peculiar effect upon the distribution of plants since 

 the glacial period, has been produced by the configuration 

 of the earth. North America has a much greater variety 

 of trees than has similar parts of the Old World though 

 from the evidence of fossils we are forced to conclude 

 that before the glacial period Europe was in no respect 

 deficient in such vegetation. When the ice invaded north- 

 ern regions, however, the .\merican species were able to 

 escape by moving southward, but in Europe the escape 

 of the \egetation was cut off by high moimtains extending 

 across their path and thev conse(|uently perished. 



Non-effectiveness in life is not so nnich a misfortune 

 as it is a positive and definite fault on the part of the 

 individual. The man who is always dawdling along a 

 journey and never arriving at his destination needs an 

 absolute reorganization of his life. Now to a very great 

 deyree the non-effective person accepts his defeats and 

 failures as a part of the er.tablished order of things, 

 when in realitv. they are just as entirely his own fault 

 as would be falsehood or anv other sin. One has simply 

 no mfiral right to be non-effective. — Lilian Whiting. 



