38 
is A. Canadensis, A. agrestis. The Cheetodontes are there except 
Brauntoni. The Argophylli have argophyllus, cibarius, inflexus, Utah- 
ensis, Purshii. There are A. atratus and Salmonis, malacus bisulcatus, 
crassicarpus. The Hamosi have sylvaticus, Mulforde, Howelli, dre- 
ranolobus, Arthuri. $ x 
. The Eastern Great Basin region has the usual Homalobi and 
humistratus; also A. debilis, jejunus, serpens, andinus, Canadensis, 
agrestis, megacarpus and Brandegei ‘The Argophylli have argo- 
phyllus, cibarius, Utahensis, Purshii, The Galegiformes Drummondii 
and scopulorum, 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 Mogoilon region has among the Homalobi A. humillimus 
montanus and humistratus; also gracilentus, mollissimus, Feensis, 
Phoenicis. EE 
: The Sierra region has among the Homalobi Californicus, inversus 
and stenophyllus and campestris. There are also A. Hookerianus, 
Bolanderi, platytropis, obscurus, Canadensis egrestis, Austins. The 
Argophylli have Webberi, iodanthus, Utahensis and Purshii. The 
Hamosi have Congdoni, Andersoni, sylvaticus, lentiformis and Lemmoni, 
The Mexican plateaus and Arizona region have on the peaks few 
species. 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. 3 
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- 
perate on the mountain slopes and exterminated it on all the lower 
ranges at the south, there being little left of this life zone south of 
the Mogcllons. 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 Sierra Madres 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- 
ate, but the Astragaline flora is meager, This is another eonfirmation 
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, while many 
species at the north are Spruce zone plants that have acquired a 
Middle Temperate tolerance, such as A. agrestis, andinus, elegans, 
aboriginum, 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 innumerab!e and isolated climatic 
regions differing greatiy in humidity, soil and exposure, ard admirably 
suited to varied plant forms and therefore the species of Astragalus 
are the most numerous of any life zone. In Glacial times if there 
was any such area at all it must have been far south in the Irapuato- 
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, Nuttallianus and triflor:s 
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 
