CONTENTS. 



PAGE. 



Introduction _, 



Certain Features in the Attempted Classification of Roots 9 



Scope of the Study and Methods 10 



Environment of Roots i -, 



Leading Characteristics of the Soil 12 



Tumamoc Hill 12 



Flood-plain of the Santa Cruz river 12 



West Wash i , 



The Bajada i ^ 



Moisture in the Soil 15 



Tumamoc Hill j c 



The Bajada j ^ 



The West Wash 18 



Flood-plain of the Santa Cruz river in 



Temperature of the Soil 20 



Record of Thermograph: 15 cm. depth 20 



Record of Thermograph: 30 cm. depth 21 



Soil Temperatures: 2.5 cm. depth 22 



Summary of Environmental Conditions 23 



Root Habits of Desert Plants 25 



Summer Annuals 25 



Amaranthus palmeri 25 



Anoda thurberi 26 



Aster tanacetifolius 26 



Boerhaavia sp 26 



Cladothrix lanuginosa 27 



Datura sp 27 



Ditaxis humilis 27 



Dysoda papposa 28 



Euphorbia glyptosperma 28 



Kallstroemia grandiflora 28 



Pectis prostrata 29 



vSolanum eUeagnifolium 29 



Trianthema portulacastrum 29 



Vicia sp 29 



A\'inter Annuals ,0 



Amsinckia spectaljilis ^o 



Astragalus nuttallianus 31 



Bowlesia lobata -,1 



Brodi;ca capitata 31 



Daucus pusillus ^3 



Eritrichium pterocaryum and Harpagonella palmeri 33 



Erodium cicutarium 3^ 



Festuca octoflora and Hordeum rnurinum 34 



Gilia bigelowii 34 



Malva borealis 35 



Medicago denticulata 35 



Mentzelia albicaulis 36 



Microseris linearifolia 36 



