34 SILVA OF NORTH AMERICA. 
ment or an understatement. The precise records of his expeditions 
are therefore valuable, and in The Commerce of the Prairies is found 
the most trustworthy record of the condition of commerce in the 
west before the great midcontinental plains were crossed by rail- 
roads. During his residence in Mexico Mr. Gregg devoted some 
attention to botany and discovered a number of undescribed plants. 
OLEACEZE. 
Greggia, a genus of cruciferous herbs of western Texas and north- 
ern Mexico, was dedicated to him by Asa Gray. In 1846 Gregg 
accompanied General Wool’s division of the United States Army to 
Chihuahua as guide, and later marched to Saltillo with General 
Butler. He is believed to have died in California in 1850 (Garden 
and Forest, vii. 12). 
EXPLANATION OF THE PLATE. 
Puate CCLXII. Fraxinvs GRreaeii. 
1. A fruiting branch, natural size. 
ou PR O& bo 
. Vertical section of a fruit, enlarged. 
. A seed, enlarged. 
. An embryo, much magnified. 
. A leafy branch, natural size. 
