38 



ts A. Canadensis. A. agrestis. The Ch£Etodontes are there except 

 Brauiitoni. The Argophylli have argophyllus, cibarius, inflexus, Utah- 

 ensis, Purshii. There are A. atratus and Salmonis, malacus bisulcatus, 

 crassicarpus. The Hamosi have sylvaticus, Mulforda), HowelU, dre- 

 ! anolobus, Arthur!. 



The Eastern Great Basin region has the usual Homalobi and 

 humistratus; also A. debilis, jejunus, serpens, andinus, Canadensis, 

 ngrcsiis, nie?;acari)us and Brandegei. The Argophylli have argo- 

 phyllus, cibarius, Utahensis, Purshii. The Galegiformes Drummondii 

 ;ind scopulonim. the latter a late immigrant. There is A. calycosus. 

 The Western Great Basin has in addition to these given A. platytropis, 

 stenophyllus, tegetarioides, aboringum and obscurus. 



The Mogollc-n region has among the Homalobi A. humillimus 

 montamis and humistratus; also gracilentus, mollissimus. Feensis, 

 Phoenicia. 



The Sierra region has among the Homalobi Californicus, inversus 

 and stenoi^hvllus and campestris. There are also A. Hookerianus, 

 Bolanderi. platytropis. obscurus, Canadensis agrestis, Austina-.. The 

 Argophylli have Webberi, iodanthus, Utahensis and Purshii. The 

 iiamosi have Congdoni, Andersoni, sylvaticus, lentiformis and Lemmoni. 



The Mexican plateaus and Arizona region have on the peaks few 

 Bpecies. There are A. humistratus, Hartwegi, militaris and strigul- 

 osus in the border, and farther south the Strigulosi and Mollissimi 

 abound on the plateaus, and the Flexuosi are scarce. 



The total Middle Temperate species are 121 or 28 per cent of the 

 whole. 



The lower Temperate climate which has prevailed throughout 

 the floor of the Great plateau at the south except in the Arizona region 

 since the drying, up of the great lakes has isolated the Middle Tem- 

 peraif' on the mountain slopes and exterminated it on all the lovrer 

 ranges at the south, there being little left of this life zone south of 

 the M;.2-''!!ons. There is a little in lower California on the San Pedro 

 Martir. and in the San Bernardino Mountains California, besides the 

 large area in the Sinrra Madrps mentioned. The floor of the Great 

 Plateau north and northwest from Cache valley Utah to the Blue 

 mountains, and northeastward to the Saskatchewan is Middle Temper- 

 ■^te, hilt the Astr.^g^line flora is meager. This is another confirmation 

 of the fact that a cool climate and moderate humidity are not con- 

 ducive to species differentiation. Over half of the Middle Temperate 

 species are the products of isolated areas at the south, v/hile many 

 species at the north are Spruce zone plants that have acquired a 

 Middle Temperate tolerance, such as A. agrestis, andinus, elegans, 

 aboriginura, montanus, tenellus, Hookerianus, Bourgovii. 



LOWER TEMPERATE LIFE ZONE. 



The extinction of the Middle Temperate flora on the floor of the 

 Great Plateau, as far south as the upper limits of Utah, by the lower 

 Temperate has left a vast area with inunmerab'o nnd isolated climatic 

 regions differing greatly in humidity, soil and exposure, and p.dmivably 

 suited to varied plant forms and therefore the species of Astragal'i?; 

 are the most numerous of any life zone. In Glacial times if thore 

 was any such area at all it must have been far south in the Irapnato- 

 Guadalajara region of central Mexico. That there could hardly have 

 been such a region is forced upon us by the character of the species 

 and their distribution. A. Bigelovii, Humboldtii and mollissimus of 

 of the Mollissimi; A. racemosus. Hartwegi, Nuttalliauus and triflor;? 

 are the only species with anything like general distribution, while all 

 but the last two are of Middle Temperate, and the last of Tropical 

 origin. The great diversity of the species from Arizona northward 



