TABLE OF CONTENTS. 
Page. 
Letter of transmittal.... 2.22.0 ....0 22 cee cee cece cece ee nec ce cee eeecneees UI 
INtroductory NOt61oc2560 4. one cieradad neude etaewdrowacurdeuce deeede hetteceahs 133 
POUNCE EY aso tes as earache attest asic usenee came elem aveieiels ue 133 
Formation of the sand-hill region........... 02.20. 000200 eee cee eceeeceeeces 135 
Topography and floral districts...... 2.2.2... 02 2220 eec eee cece cece cece cece cues 136 
Middle Loup Valley...-- 2.22222... .c00 cece cece ec een e ee ce cenecncneecnance 136 
Disa River Valley eect2 26 cence oe os seek ae Sae ne cmeand 136 
The barren sand hills.............. cee a ioe Sitecee ewe wets Stee tae ata 137 
The dry valley sand hills.......22. 222.22. cee cece cee cece cone cece cecees 137 
The wet valley sand hills... 20.2... 002.022 cee cee cee eee eee ee nee nee 137 
Climatic conditions ....... 0.020022 2 cece cen eee cee cee cee ce eeee cnee cess 138 
BC U0) Sane a do ote PRO eS en ROE ee PC ne ee ee de 139 
Sand-hill vegetation .... 2... 00.000 cee cence cee ce eee cece cone cone eeee 139 
Dry-valley vegetations esesre es cireceraceaced ane yeikicke hoes eaecsbe dees 140 
Wet-valley veretation .<cccsntec. tc ccecnsdesbdiadncsedcaeateaweeesuaeess 140 
AQGSIC HOPE 1 vhost dee asescckecienweewusecs cccisk Ceased cee sietecece tock 140 
WV COOB 222 aG oceans eee see en ene aoe eae ree ee eeeees 141 
Native trees and shrubs. ........---- 2-22 eee eee cee ene ee ee cone enone 141 
Native forage plants ...... 0.2.2... .200-. 000 eee ee ee ee ee 142 
BlOCK PAISiINg oc5Si ot edes eee ood eon cee ee enne Oe eoea een men tee eas 143 
A GriCd) Fur6..2 55 ccoee rea tsu ecoeseuwedesedeeiees ceeeeeteueeesucwes weaeeews 144 
Hetoresting tho sand Nilld)..h253cceetecevriins coeds ness oaemeseciesenueereeunSs 145 
Catalopae of speciesep 2255.51 55ie tse otis see ascents inesastecwodssseceeses 147 
Catalogue of specimens.......---.--- 2-22 eee ee eee ee ene Cee eee eee ee 195 
LIST OF ILLUSTRATIONS. 
Facing page. 
PLATE I. Map of part of the sand-hill region of Nebraska, illustrating the 
route of PiA. Rydberg in 1893 22222.64.20202 wees ceccaccseese ote I 
PLATE II. Carduus plattensis Rydberg... ....---------- 2-2 eee e ee eee eee eee 167 
Fic. 1. Diagram of the wet valleys in the sand hills. ................2..2-22. 138 
