1920] PALMER, CANYON FLORA OF EDWARDS PLATEAU 235 



most remarkable of all, and indeed one of the last trees one might expect to 

 find in such a region, is the Bald Cypress {Taxodium distichiim) , which often 

 grows abundantly and of large size about the deeper water holes. 



This tree, which is most at home in the deep swamps of Mississippi and 

 Louisiana, a region of very abundant rainfall, has here adapted itself in a 

 remarkable manner to the peculiar conditions of a semi-arid country. Here 

 too, although there are no swamps, it actually grows with its feet in the 

 water: for it is never founl more than a few yards back from the margin of 

 the pools, and while on the uj)per side it is firmly anchored to the solid, often 

 rocky, bank, a precaution made necessary by the occasional destructive 

 freshets, on tlie other side its roots are thrust deep into the permanent pool 

 of life-giving water. Here it has no use for the peculiar aerial root cones or 

 knees, that are so conspicuous and characteristic a feature of its gro^^lh in 

 the swamps, and it has entirely discarded them. The general habit of the 

 tree is stockier, the branches larger and more wide-spreading and the crown 

 consequently lower and broader than fu:thereapt. The base, while usually 

 well buttressed and hollow^ near the ground, has never the exaggerated pro- 

 portions commonly seen in swamps. Cypress occurs along the Medina, 

 Sabinab Frio, Nueces and Devils Rivers and a number of smaller streams, 

 from the heads of the canyons to the point wliere they leave the plateau. 

 After they descend into the Rio Grande Plain most of the streams cease to 

 flow perennially. Their waters sink beneath the gravel, except for short 

 distances or in occasional pools, and Cypress Is not found in that region. 



The high bluffs that wall in the wide canyons afford considerable protec- 

 tion from the dry w^inds and scorching sun and along their bases and ledges 

 there is usually a deeper accumulation of soil and a certain conservation of 

 moisture. Consequently there is a more vigorous and varied gro\\i:h of 

 trees and shrubs here than in the open valley or on the rocky table-land 

 above. One of the interesting trees of such situations is Lacey's Oak (Quer- 

 cus Laceyi), a species of White Oak that appears to be limited to the canyons 

 of the Edwards Plateau. It is a small sized tree, rarely more than thirty 

 or forty feet high, with a trunk seldom a foot thick; the bark on old speci- 

 mens is deeply fissured; the trunks often crooked and not infrequently sev- 

 eral spring from a common base. It can be recognized at some distance by 

 the peculiar l)luish or smoky hue of the foliage, unlike that of any other Oak. 

 The Mexican Buckeye (Ungnadia speeiosa)^ Western Red-bud and the 

 Texan Arbutus, the Madrona of the Mexicans, are likely to be fgund here 

 with many other interesting species. Much of the high rocky t^ble-land of 

 the divides is covered by a more or less dense gro\\i:h of scrub. The Shin 

 Oak {Qucrcus cuinulata) is in some sections the most common species over 

 thousands of acres, A stunted form of the Live Oak often grows with it. 

 The Mountain CeJar {Juniperus vi:xicina)^ the Mexican Persimmon, and 

 the Small-leafed Adelia {Forestiera puhescens) are quite abundant. Yuccas, 



various species of Cactus and the low thorny Cat's Claws or Acacias mingle 

 with them and predominate over the more exposed portions. 



Having thus hastily glanced at the physiography of the plateau and the 



