Chap. IV. VALLEY OF MESILLA. 475 
different species of cactus had flowered from the beginning 
of the month. 
I must not pass unnoticed a phenomenon I observed 
here repeatedly, which will interest those who study the 
physiology of plants. It had not rained for many months ; 
the loose sand was dry, and was daily heated by the sun ; 
in spite of which I observed seeds germinating in this 
very sand. This phenomenon is connected with the 
general question, by what natural means vegetation is 
maintained in a country without water, with an exceed- 
ingly dry atmosphere, and with a periodical absence of all 
rain for six months. 
Early in June we started for California, following, with 
a few slight deviations, the road through the basin of the 
Gila, known by the name of Cook's Route. At Fort 
Fillmore our waggons were conveyed across the river on a 
flat boat. The mules were obliged to swim over, which 
was not easily effected, and many of them were carried 
down the stream ; others returned back to the shore when 
half way across, and others still stuck fast in a quicksand. 
We thought ourselves fortunate that the whole drove was 
brought over without loss. A German, who had joined 
our caravan on this occasion, sank up to his waist in a 
quicksand, and had to be pulled out with cords. I have 
said above that these sandbanks render the Eio Grande 
exceedingly dangerous. 
On the other side of the river we found ourselves in the 
valley of Mesilla. The political interest connected with it 
has been mentioned in a former chapter. This village has 
great advantages of soil, being fertile and easily irrigated. 
The beautiful appearance of large tracts of the valley de- 
ceived and disappointed us, looking as if covered with rich 
grass, which proved to be only a plant of the family of 
