EELATIONSHIPS OF ALABAMA FLORA. 39 



the State: JVeviumi cdahamenMs^ Crotmi alahainenx'tx^ and Trichomanes 

 ixdersu. This poverty in endemic forms is easily explained by the 

 absence of any serious obstacles to plant migration from and to all 

 parts of the eastern section of this continent. The gradual descent of 

 the Allegheny Mountains to the Coastal plain rendered the influx of 

 plants from the north and east easy. The oldest types flourishing on 

 the most ancient strata succumbed gradually to the vicissitudes of eons 

 of time and gave way to later invaders. Completely open on the east 

 and the west, the denizens of the plant world from these directions 

 found no hindrance in peopling the new soils of the secondarj^ 

 (Mesozoic and Cenozoic) formations, after their rise above the water. 



RELATIONSHIP OF THE ALABAMA FLORA TO THAT OF ADJOINING 



REGIONS. 



It results from these conditions that the plant-covering of the State 

 coincides closely with the flora of the adjoining regions. In its south- 

 ern portion it is very intimately related to the flora of western Florida, 

 Mississippi, and eastern Louisiana, equally so to that of the maritime 

 plain of North and South Carolina and Georgia, and in a less degree 

 to that of western Louisiana and eastern Texas. In its central parts 

 the same close connection exists with the flora of the middle region 

 (Piedmont region) of these States and with that of southern Arkansas. 

 The flora of the northern part of the State, wdth its mountains and 

 the Tennessee Valley, presents a similar relationship with the flora of 

 the Allegheny ranges south of the Potomac River, below an elevation 

 of 2,000 or 2,500 feet above sea level, and with that of the southern 

 extension of the Cumberland Mountains and the rim of the Highlands 

 of Tennessee. 



RELATIONSHIP OF THE ALABAMA FLORA TO FOREIGN FLORAS.^ 



EASTERN ASIA. 



Asa Gray first directed attention to the intimate relationship exist- 

 ing between the flora of eastern North America and that of eastern 

 Asia, particularly^ that of Japan. ^ The eastern Asiatic element is in 

 this part of our continent most pronounced southward. It is here 

 most strikingly manifest in the arboreal and shrubby vegetation of the 

 numerous genera of the catkin-bearing families, such as walnut, chest- 

 nut, oak, beech, hazlenut, iron wood, hornbeam (Ostrya), willow, wax 

 m3a'tle; and of the coniferous family, such as pine, hemlock, cypress 

 (Chamaecyparis), savin (Juniperus); to which are added elm, mul- 

 berry, linden, pear, plum, service trees (Amelanchier), maple, witch 



'In this discussion the introduced and immigrated plants occurring in Alabama and 

 the genera represented only by cosmopolitan species inhabiting the temperate and 

 warmer regions all over the globe are disregarded. 



^Asa Gray, Memoirs N. Y. Acad., vol. 6, part L 1859. 



