CONTENTS. 
PAGE 
TMGPOMUGEION 2.50 diets ieee wa cee aan om oes ane Seine eee a ae he 5 
Geography and Topography of the Santa Catalina Mountains....................- 6 
Vegetation of the Santa Catalina Mountains............... 00 cece eee ects 11 
The. Desert REGION ccc vs sada eds tad maaees scones hoe Ketadoed cea Glen ad 15 
The Upper Bajadassiec:ocscascadscosdna pes tte eoeGs Qaw det wows Asa wad ys 15 
The Desert Arroyos and Cafions............. sec e eee ee ee eee eee nees 19 
The Lower Desert Slopes........... 0.0 ccc ccc cee cect eee e cee nt eee eeeee 22 
The Upper, Desert Slopes... esses sa. o's ceneares 24 Ase ei see Seek Lataiene eee ewes 23 
Che Prema RegtONs i523. a:ato bbe css aicies apiyasiy cen dealivs Bunterg a adc pers hare arene 24 
The Lower Hneinal,. 0 s54 71s ssedieg + o4 pice dewaining 96 AGERE aR RESTS es 25 
The: Upper: Hincitial 10 ss0-c teense oa posed daveaareni mee dd eae ee Fiancee 27 
The. Forest Regions so: xieastssaaes's reas staan oie adie i ewae oaks eese es 29 
Whe, Pine PGrest ssssse ates oe setae ae ae ee Oa mee One sek eee eae 31 
The Bir HOreat ses. saan veataica wee sciatic cbs Gece RE RR A Re odo ped Bas Sade 33 
Flora of the Santa Catalina Mountains............. 0.0. eee cece cee eee ee neee 36 
Phytogeographic Relationships of the Flora............ 00sec cece eee e cence 36 
‘The Desert Ploras:cskas saagne aounnsee ee owada ss ex isgen.ws aque eee uurdens 36 
Whe: Enciniall PGi ab cscisieidiece! s25e,axzecedeh ayia cdusicace soln idavahace eve) couininia tera or@ lalava, v4. aoayausne 38 
The Forest: Horas sss awa eed ances e jee, oa Mae LAKE Bebe Crane 39 
List of Characteristic Species........ 0... cece eee cece eee eee eee eee enenees 41 
Climate of the Santa Catalina Mountains. ........... 0.00. cece cee cee cee eeeeenees 46 
Rainfall..............00. pein Slaven a  AsuiGuebalt ca. couctendeaiva cn sai na to ance reaae 8 48 
Seasonal Distribution of Rainfall........... 0... 0c cece cee eee eee ene ees 48 
Altitudinal Increase of Rainfall................ 0. cc cee cee cece cece eeeees 51 
Soil Mosture: sc. dee ot Saad ecg dich hc eke pi noe o Reese dona otvcn Fe 4 Rats 59 
VV pOra tin ss scese wiaiise' sg eoaeaiete owe Renels eda Wels Sate Nass Sree eos op apace 63 
| MUM byes s sees 5 hee tres aewss Res Syne 4 Se arena arars -qbaey 00S ReaRe aN. eG anasea ocauabene 67 
Temperature sss cos yacis seo piso we ewinieieg eo aaee Ss +e Glew Se swReee ea buleles ve eles 69 
Length of Frostless Season...... 0.0... cece cee cence cect teenenenaee 70 
Normal Altitudinal Temperature Gradient. ........... 0... c ccc cence eee 75 
The Absolute Minimum of Winter.................. ccc cece e eee ee eeeee 79 
Departures from the Normal Temperature Gradient due to Cold-air Drainage 82 
oil Pemperatre oie .c versises ae vttstsies ais weaicie's evi nage mea eae ea Say eee wees oes 86 
Correlation of Vegetation and Climate in the Santa Catalina Mountains............ 88 
The Normal Altitudinal Gradient of Vegetation................00cccseeeeeece 88 
The Vertical Distribution of Individual Species...................0:00 eee 89 
Physical Factors Involved in the Determination of the Normal Altitudinal Gradient 
of Vegetation... 0.6... cee cece cece ces Be ait ws Rete aura oa noes 91 
Moisture Factoteee: .csccs0058 cas deed oo% Mae Ne Cane eb eadw Te eA Paes 92 
Temperature: HACtOrs s:sccescsscce Sasi s dig ateg we ee Rae eee Sians vs Gains Foe SS 94 
The Réle of Topographic Features in Determining Departures from the Normal 
Altitudinal Gradient of Vegetation........... 0.0 ccc ccececcceeeences 97 
The Réle of Slope Exposure............ ccc cece ete ee tree eteeeeeseeeee 97 
The Réle of Streams and Flood-plains ................ ccc ceecececeeeees 104 
The Réle of Topographic Relief...... 0.0.0... cc cece cece eee ete eee eees 107 
General Conclustonsssiieo5i5. esasec cases eeaei 4% Rowe oo FRR S45 ose wie eC eceawle alee 109 
