74 ROYAL SOCIETY OF CANADA 



EeASONS why THE LiTTLE ElVER PLANTS RESEMBLE THE CaRBONI- 

 PEROUS MORE THAN THE DEVONIAN. 



In the modem world extremes of climate in different parts of the 

 world are very marked and the vegetation corresponds to these differ- 

 ences. A totally different flora prevails in the West Indies from that 

 found in eastern Canada, though only twenty degrees of latitude divide 

 them. In going west from the Mississippi valley to the arid plains 

 whence its great tributaries flow, a similar great change in the flora 

 occurs, though from a different cause, and it may be well to consider 

 how far corresponding variations in climatic conditions may have gov- 

 erned the spread or withdrawal of certain types of plants from a given 

 region of the earth's surface in Palseozoie Time. Too little is known of 

 the adaptability of the plants of that early time to climatic conditions, 

 to enable us to indicate in any but the most general way, the result of 

 changes of climate on these floras. 



Any one who has been in tropical or even south-temperate climates 

 will note how readily the soil of the uplands assumes a ruddy colour 

 owing to the oxidation of the iron with which it abounds, while the ac- 

 cumulated vegetable matter of the lowlands and hollows, gives rise to 

 large bodies of dark soil. To the Spanish Creole the former is tierra 

 colorada the red soil, and the latter tierra negra the black soil. Prof. W. 

 0. Crosby, late of the Institute of Technology, in Boston, has very well 

 described the way in which the former originates.^ 



The writings of Jas. Hall, W. B. Scott, C. Schuchert and many 

 other geologists will enable one to form a conception of the mild climate 

 that prevailed in the northern hemisphere in Ordovician and Silurian 

 times, and several writers have shown the existence of land plants even 

 in the former Age, but so far, except at St. John, no important flora of 

 that time has come to light; the majority of geological deposits on the 

 land are thin, incoherent and easily swept away, and it is not surprising 

 that the farther back in time we seek for such deposit the more rare they 

 become; the exception at St. John is the result of the deposition of del- 

 taic sediment over' an area of the earth's surface already weakened by a 

 deposit of several thousand feet of Cambro-Ordovician sediments that 

 had not been strongly consolidated. Like the tierra negra these sedi- 

 ments were darkened by an abundant vegetation derived from the land 

 plants that flourished at the time. 



In a paper read before the Natural History Society of New Bruns- 

 wick a year to two ago, the writer published a map showing his view of 

 the relation of the Little Eiver Group to the neighbouring terranes, and 



1 On the contrast in color of the soils of high and low latitudes ; also Proc. 

 Boston Soc. of Nat. Hist., Vol. XXIII, pp. 219-222. 



