48 DAVENPORT ACADEMY OF NATURAI, SCIENCES. 



on an obscure, thickened ring at the throat of the invohicre, with small 

 intervening lobes, barely distinguishable under a lens, but plainly indi- 

 cating an obsolete perianth. In this view of the case, the whole ques- 

 tion is at once cleared up ; an anomalous monotypic genus is merged 

 into its nearest allied genus, and Lastarricea Chiletise, Remy, becomes 

 C/iorizafithe Lastarricea, appropriately closing up the genus with its 

 most reduced species, and naturally connecting it with succeeding 

 genera of a still more reduced type. 



GEOGRAPHICAL DISTRIBUTION. 



The peculiar geographical distribution of the genus Chorizanthe is 

 deserving of special consideration. Thus, while agreeing in its general 

 habit with the closely allied and extensive genus Eriogonum Tand with 

 fully one-fourth as many species), it has a much more hmited range, be- 

 ing mainly confined to the arid coast and desert regions of California. 

 Out of the twenty-eight species here recognized, only three extend as 

 far east as Southern Utah, and the state of California includes within 

 its present boundaries all the known North American species. The 

 exceptional case of C. Lastarriaa, also occurring in similar districts on 

 the South American Pacific coast, without any known intermediate 

 locality, can hardly be accounted for on any general law of vegetable 

 distribution, and would seem to favor the view of accidental transpor- 

 tation by human agency ; but its wide prevalence throughout all South- 

 ern California, and the still more remarkable analogous case of Oxytheca 

 dettdroidea, having a similar disconnected range, and without any spe- 

 cial provision for eftecting accidental transportation, is opposed to such 

 a supposition. But, leaving out of view these anomalous cases, it is 

 more to the present purpose to enquire what are the conditions of soil 

 and climate in which this particular genus finds a congenial location; or, 

 in accordance with the prevailing philosophic views, what is the natural 

 environment that determines their peculiarities and rigidly defines their 

 geographical limitation? 



Now, the main feature of the California coast climate, as well as the 

 adjoining desert districts to the east, where this genus is more or less 

 prevalent, is a winter rainy season, not too cold to check ordinary 

 growth, succeeded by a dry, warm season, favoring only a limited 

 development of plants adapted to arid conditions. Hence, all an- 

 nual plants (including Chorizanthe) require to have their vigorous 

 growth fully established during the season of moisture, and their subse- 

 quent development, if prolonged into the dry season, is maintained by 



