214 BOTANICAL GAZETTE [September 



mountains 



doubtless be occupied by Douglas spruce were they situated at 



greater elevation, chiefly 



mountains 



on the campus of the University of New Mexico at an elevation 

 of only 5200 ft., but they are carefully irrigated , and the Douglas 

 spruces are in the shade of cotton woods. The storksbill (Er odium 

 cicutarium) grows in the mountain canons and at an elevation of 

 5000 ft. in the valley. In the former situations it is in blossom 

 nearly all winter, often directly beside a snowbank, and doubtless 

 because of the snowbank, while those in the valley do not bloom 

 until the May or July rains. 



Fallugia paradoxa is a most interesting plant in this regard. 

 As mentioned above, it is a very characteristic plant in the arroyos 

 of the mesa and its edge down to less than 5000 ft. It grows at a 

 lower altitude than this farther south, and doubtless would here 

 were there lower altitudes. Now these arroyos are the hottest 

 places in this region. Their sands reflect the desert sun's glare 

 and the banks obstruct the breeze. Yet this same Fallugia forms 

 thickets on the Sandia Mountains at an elevation of over 9000 ft. 

 on steep slopes facing the southwest, and it grows at all altitudes 

 between. On a basis of temperature control, this distribution seems 

 inexplicable. But these arroyos are the least xerophytic places 



The soil at the depth of a foot or two is always 



mesa 



moist, due to the 



th 



two or three times each summer and the sand conserves this and 

 the rain most thoroughly. On the contrary, those steep south- 

 western slopes are the most xerophytic places in the mountains, 



the exception of course of bare rock. But on account of 

 greater rainfall, these most xerophytic places of the mountains are 

 about as moist as the least xerophytic places on the mesa, and 

 Fallugia paradoxa occupies both situations. 



On an ascent of the mountains made on May 8, 1910, the oaks 

 in the lower parts of the canons were found in full leaf, and their 

 blossoms gone; a little higher they were just leaving out and 



ming; at the top of the 



Again 



on October 6 the leaves were still green and vigorous at the base 



