62 IOWA ACADEMY OF SCIENCES. 



NOTES ON THE FLORA OF TEXAS. 



BY PROF. L. H. PAMMEL, AMES. 



In 1888 and 1889 the writer had the pleasure of spending a few months 

 of two summers in studying a disease of cotton commonly known as 

 Root-Rot of Cotton. Incidentally some attention was given to the phieno- 

 gamic floi-a of the State. 



The territory embraced is Central Texas, along the Houston & Texas 

 Central R. R. from DenisoQ south to Hempstead, as far west as San Marcos, 

 in Hays county, and Marble Falls, in Burnet county. Soil and climate 

 vary greatly, which is well shown by the character of the vegetation. The 

 most important feature in the northern part is what is known as the Central 

 Black Prairie region, which extends south through Ellis, and the northern 

 part of Navarro counties. The soil of this region is mostly what is termed 

 "black waxy" — an extremely tenacious soil, but in dry weather it be- 

 comes hard and cracks, sandy soil only occurring along streams. The char- 

 acter of the vegetation of the former is quite uniform. Orindelia inuloides, 

 Aplopa2}pus ciliatns, Eryngium leaveyiworthii, Andropogon saccharoides, 

 Xanthium eanadense, Centaurea americana, Sabbatia oarnpesiris are 

 abundant everywhere. A white rotten limestone underlies the region. 

 Frequent outcrops occur. Near river courses Quercus durandii is common. 

 On the sandy soils Quercus nigra, Juniperus virginiana, Oilia coronopiJoUa. 

 In the Central Black Prairie Region further west in Williamson, Travis and 

 Hays counties Prosojns juliflora is common, becoming more so further 

 west. Along the river bottoms of the Red and Brazos rivers the alluvium 

 is very deep. The soil has a red color and is covered with magnificent trees 

 of Eicoria pecan, Juglans nigra, Platanus occidcntalis and Populus moni- 

 lijera. 



Along the Trinity river the soil has an entirely different aspect. The 

 alluvium is of a grayish color owing to the source of the river which is a 

 little west of the central black prairie region. Cdtis mississippiensis, Pop- 

 hdus monilifera, Juglans nigra, Hapindus marginatus are abimdant. South 

 of Navarro county the surface of the country is quite uniform; in many places 

 there is scarcely any drainage. The soil is sandy or loamy, with a hard pan 

 underlying it. Here and there are prairies with good and more or less 

 black, sandy soil. Quercus obtusiloba is abundant. Qucrciis virens occurs 

 in gulf prairie region in Washington county. This is also a tenacious soil. 

 Sabbatia camjicstris, Etcstoma russellianum, are common in this region along 



