jjj BOTANY. 



for the whole 24 hours and making it the basis of a calculation of the daily 

 loss of the plant, the first mentioned specimen of Artemisia appears to have 

 exhaled 9 ounces of water daily, or an amount equal to three-eighths of 

 its weight. Even in the last trials later in the season, when leaves and stems 

 had probably their fullest dryness and hardness, with one of the most waxy 

 and scurfy of the Obiones, and moreover under atmospheric conditions more 

 favorable for the plant, the loss was at least half as great. 



Notwithstanding therefore the apparent want of moisture in the soil, it 

 must be the reservoir from which vegetation draws its entire supply. The 

 loose character of the deposits which fill the valleys and form the foothills 

 not only allows a ready passage for the roots to any necessary depth but 

 especially, through the force of capillary attraction, compels the retention 

 or absorption from beneath of a sufficient amount of water for the tem- 

 porary extraordinary needs of these perennial species. And this natural 

 resource of the vegetation must be taken into account as greatly favoring the 

 possibility of the successful introduction of orchard, vineyard or other tree- 

 culture in these at present desert territories. 



Conclusion. The present condition of the Botany of our western flora 

 is such as to render a satisfactory determination of the species of any col- 

 lection a matter of some difficulty. The descriptions of many of the genera 

 and species are scattered, without clue to guide in the search for them, 

 through numerous volumes of government reports and periodical publications 

 of this country and of Europe, not always readily accessible. The synonomy 

 is somewhat confused, and in the case of various genera revisions are much 

 needed, with a collation of all the existing materials, a work which is going 

 on under the hands of Dr. Gray, Dr. Engelmann and others. 



In the examination of the present collection use has been made almost 

 exclusively of the herbariums of Dr. Gray, Dr. Torrey and Prof. Eaton, which 

 are the richest in original and authenticated specimens of western species 

 and to which, with their accompanying libraries, free access was most gener- 

 ously given with every facility for study and comparison. So far as the 

 work has been performed by others the names carry their own sufficient 

 authority. As for the rest it can only be claimed that care and eflfort have 

 not been spared to secure correctness. 



The trouble experienced in making available the authorities upon western 

 species gradually suggested the extension of the Catalogue beyond the usual 



