THE NORTH AMERICAN DESERT FLORA. 345 



hard or spiny envelopes. In certain cases, especially among Cactuses, 

 proliferous shoots, easily detached and quickly rooting, serve the pur- 

 pose of seeds in providing for the continuance and distribution of 

 species ; and in such instances the very remarkable and significant 

 fact may be noted, that the fruits generally prove abortive, or even 

 revert to the condition of proliferous shoots. 



In the accompanying list a great disproportion in the represen- 

 tation of different Natural Orders and of particular genera is very 

 plainly exhibited, and there is complete absence of some Orders and 

 genera usually represented in north temperate climates. 



Tlie list contains 188 species; Dicotyledons are represented by 169 

 species, included in 48 Natural Orders and 144 genera ; and Monoco- 

 tyledons include 19 species, comprised in 4 Natural Orders, and 10 

 genera. The Natural Order Compositce possesses the largest number of 

 species, viz. 44, or nearly one-fourth of the whole phanerogamic flora. 

 Leguminoscs (which includes most of the dwarf trees and larger shrubs) 

 comes next in point of number, with 25 species. Other prevalent 

 Natural Orders are very variously represented. Of the lower Orders 

 (which are not included in the following list) Lichens only are fairly 

 represented. 



Myosurus minimus, L. SesuviumPortulacastrum, Condalia spathulata, Gr. 



Berberia trifoliata, Mori- L. Microthamnus ericoides, 



cand. Lewisia rediviva, Pursh. Gray. 



Argemone mexicana, L. L. brachycarpa, Engel. Karwinskia Humboldti- 

 Eschscholtzia Douglasii, Fouquiera splendens, -£'«_5'. ana, Zmco. 



Hook. Malvastrum exile, Gray. Adolphia infesta, Meisn. 



Corydalis aurea, Willd. M. coccineum, Gray. Janusia gi'acilis. Gray. 



Sisymbrium caneseens, M. Monroanum, Gray. Holaeantha Emorji, Gr. 



Nutt. Hibiscus denudatus, Bth. Canotia holaeantha, yorr. 



Vesicaria Fendleri, Gray. Larrea mexicana, Moric. et Gray. 



Y. argyrea, Gray. Kallstroemia maxima, Polygalascoparia,//. B.AT. 



Dithyrea califoruica, Har. Torr. et Gray. P. Lindlieimeri, Gray. 



Lepidium flavum. Gray. K. grandiflora, T. et G. P. puberula, Gray. 



L. Wrightii, Gray. Thamnosma montanum, P. Xantii, Gray. 



L. alyssoidcs. Gray. Torr. Kramcria parvifolia, Bth. 



CleomcUa angustifolia, Rhus microphylla, Engel. K. caneseens, Gray. 



Torr. Glossopetalon spinescens, Dalea spinosa, Gray. 



C. lougipes, Torr. Gray. D. Emoryi, Gray. 



Cleome Sonorije, Gray. Rhamnus croceus, Nutt. D. Frcmontii, T. et G. 



Polanisia uniglandulosa, Ceanothus Fendleri, Gr. D. Sehottii, Gray. 



DC. Zizyplm-s Pan-yi, Torr. D divarieala, BentJt. 



