3^2 JOURNAL OF THE ARNOLD ARBORETUM [vol. ii 



furnishing a porous, acid soil, it flourishes, producing tall, straight trunks 

 surmounted by a small crown of branches, frequently far overtopping the 

 largest specimens of broad-leaved species. These ancient lofty trees 

 lording it over the humbler but more widespread and dominant deciduous 

 species evidently are survivors from an earlier period in the botanical 

 history of the region. At present the young growth of broad-leaved 

 shrubs and trees has so closely invested the Pine-colonies in most placi^s 

 that there is little chance for extension or even for the replacement of 

 the stand. Only in the most sterile and uninviting spots or oc(^a- 

 sionally in artificial or accidental clearings can the young Pine-seed- 

 lings find much opportunity to develop; and it is apparent that under 

 natural conditions the species would ultimately be eliminated by its more 

 aggressive competitors. 



North of the White River, in tlie Ozark plateau, as has been indicated, 

 a somewhat different topography prevails; but the character of the forest 

 growth is generally quite similar. There is here tlie same succession of 

 heavily wooded alluvial valleys along the streams, a bordering zone of 

 bluff and ravine supporting a rich and diverse ligneous and herbaceous 

 flora, and a widesi)read upland forest composed mainly of a few deciduous- 

 leaved species. But the gradual disappearance of some of the rarer 

 southern trees and shrubs may be noted; the forest consists of fewer 

 forms, and the average size of the trees is somewhat smaller, the growth 

 in places having a decidedly stunted aspect. The prairie openings also 

 become more frequent and of larger size toward the northwest, and 

 grasses and other herbaceous plants of the western plains begin to appear 

 in them. Pine is still found occasionally in restricted colonies, and tlie 

 Red Jiniiper is often abundant along bluffs, both becoming rarer and finally 

 disappearing along the northern border. 



Over most of the level interior portions of the plateau there are but few 

 streams of consequence, much of the surface water sinking into the frac- 

 tured or porous limestone underlying the area and being carried off through 

 extensive systcMis of underground drainage and finally issuing in many 

 perennial springs, some of them of great volume, in the deep valleys and 

 canyons about the dissected margins of the region. Such surface streams 

 as occur are usually shallow, often intermittant or with currents that 

 have the curious habit of disappearing at intervals beneath the gravel 

 or shingle of their beds to reappear lower do^\Ti in pools or to ripple over 

 exposed rocky ledges. Of this character are many of the creeks and 

 branches that unite to form the head waters of the more important streams 

 that drain the region. Amongst the latter are the Current River and 

 its several forks on the southeast, flowing into Black River, tlic Gascon- 

 ade, formed of numerous branches in the central portion, flowing north- 

 ward to the ^lissouri, and towards the west the Big Xiangua and Pomme 

 de Tcrre, tributaries of the Osage. 



On the uplands between these streams there are often wide rocky 

 stretches supporting a scanty forest growth or locally almost devoid 



