NortH Haven Sanp PLaIns 577 
During 1901 annual vegetation was scarce on the sand plains, 
but it was much more abundant during 1902. The only explana- 
tion can be found by looking up the record of rainfall for June, 
which in 1901 was only .25 inch, while in 1902 it was 4.35 inches. 
More rain feil in May and July of 1901 than came in the cor- 
responding months of 1902, but June is the month when most 
annuals appear on the plains and the amount of rainfall for that 
month is therefore a criterion of the abundance of annual plants 
for the season. 
VEGETATION 
The chief forms of vegetation of this region are essentially . 
xerophytic in character, though the conditions under which they 
are produced may not be strictly xerophytic. No great lack of 
moisture exists, but the burning heat of the sun on the sand 
enables only xerophytes to persist; other plants perish soon after 
the seeds germinate. 
Andropogon scoparius grows in tufts on both the North Haven 
and Montowese tracts (see f/. 23, @) and is probably the most 
abundant of all the perennial grasses. A single patch of Andro- 
pogon furcatus occurs at North Haven. This plant has thickened 
root nodes (see f/. 27, ¢) in which food and moisture are stored 
up and carried through the winter. On both tracts Cyperus filt- 
culmis is the most common sedge, and the dead and dried tubers 
may be seen partly uncovered in many places where the plants 
have been killed through fire or some other agency. In the 
clumps of trees Poa compressa is found sparingly. During 1902 
an annual grass came up very abundantly on the sand at Monto- 
wese during the latter part of June and was probably the most 
abundant annual of the region, forming a thick carpet in many 
places. This proved to be Sporobolus vaginaefiorus, and in com- 
pany with it occurred Syntherisma sanguinalis and S. filiformis, both 
being annuals. Other common annuals growing here were blue curls 
(Lrichostema dichotomum), which was the most abundant annual 
plant on the North Haven tract, and Polygonella articulata com- 
mon to both areas. Sarothra gentianoides (Hypericum nudicaule) 
was common at North Haven, where during both seasons this 
little plant formed green patches upon the sand (see pl. 25, a): 
Among the perennial herbaceous dicotyledonous plants the milk- 
