LIST OF PLATES. 



Facing 

 „ Pagb. 



Plate i. 



A. Upper soil, adobe clay, of Santa Cn:z flood-plain, at place shown over 4 ni. 



in thickness. 



B. Adobe clay, the darker soil, overlying the caliche hardpan, with "rotten" 



caliche, broken masses of the hardpan, between 12 



Plate 2. 



(a) Amaranthus palmeri, Tumamoc Hill, (b) Anoda thurberi, Tumamoc 

 Hill, (c) Aster tanacetifolius, Tumamoc Hill, (d) Aster tan- 

 acetifolius showing, at the left, root-formation at the base of 



lateral of first order 24 



Pl.ite 3. 



Root habits of summer annuals, Tumamoc Hill, (a) Boerhaavia sp. {b) Cla- 



dothrix lanuginosa, (c) Datura sp. (d) Ditaxis humilis 28 



Plate 4. 

 Root habits of summer annuals, August, 1909. («) Dysoda papposa, flood- 

 plain of the Santa Cruz (b) Euphorbia glyptosperma, Tumamoc 

 Hill, (f) Kallstroemia grandiflora, Tumamoc Hill, (d) Pectis 

 prostrata, Tumamoc Hill, (e) Solanum elEeagnifolium, Tumamoc 

 Hill 28 



Plate 5- 



A. Root habits of summer annuals, (a) and (6), Aug., 1909. (a) Trianthema 



portulacastrum, flood-plain of Santa Cruz, (ft) Vicia sp., Tuma- 

 moc Hill. 



B. Root habits of winter annuals, (c) and (d), March, 1906 and 1907. (c) 



Amsinckia spectabilis, Tumamoc Hill, {d) Daucus pusillus, 

 Tumamoc Hill 32 



Plate 6. 



Root habits of winter annuals, Tumamoc Hill, (u) Festuca octoflora. (6) 

 Gilia bigelowii. (f) Malva borealis, showing development of root- 

 system, ((i) Medicago denticulata. (e) Microseris linearifolia.. . . 32 



Plate 7. 



Root habits of winter annuals, Tumamoc Hill, (a) Monolepis chenopodioides. 

 (b) Orthocarpus purpurascens parasitic on Astragalus sp. (c) Or- 

 thocarpus purpurascens on Lupinus sp. (d) Parietaria debilis. 

 mature plants from favorable and unfavorable moisture condi- 

 tions, (f) Phacelia tanacetifolia. (/) Plantago fastigiata 36 



Plate 8. 



Root habits of winter annuals, Tumamoc Hill, March, 1907. (a) Sisymbrium 



canescens. (6) Streptanthus californicus 36 



Plate 9. 



Root-system of Echinocactus wislizeni. (a) Portion of system showing an- 

 choring and absorbing roots in natural position, from West Wash. 



(b) Bird's-eye view of roots from which overlying soil has been 

 removed, Tumamoc Hill 44 



Plate 10. 



(a) Root and shoot habit of a specimen of Opuntia leptocaulis growing under 

 the protection of Acacia constricta, Tumamoc Hill, (b) Optunia 

 versicolor, showing habit of plant and character of environment, 



(c) Bird's-eye view of a portion of the central part of the root-sys- 

 tem of the plant shown in b. (d) This, and figures on plate 11, are 

 of one main lateral and some of its branches of the plant shown 



above 44 



Plate ii. 



Plate 10, continued; bird's-eye view of root-system of Opuntia versicolor. . . 44 



Plate 12. 



(a) Vertical and (b) horizontal extensions of root-system of Opuntia versi- 

 color, views of which are shown in plates 10 and 11, Tumamoc 

 Hill, 1907 52 



