Spiranthes magnicamporum is also apparently isolated 
from the old field-open woodland ecotype of S. cernua 
by edaphic factors. In my experience, S. magnicamporum 
has proven to be a distinct calciphile, whereas the old 
tield ecotype of S. cernua occupies strictly acidic soils. 
Only two specimens of S. magnicamporum are known 
trom areas of generally acidic soils, but the precise na- 
tures of these stations are unknown. Both could be from 
localized calcareous areas which occur in the regions in- 
volved. Floral fragrance probably further isolates these 
taxa. Pollination studies (which were not possible dur- 
ing my study) would be most useful in this group. 
These two ecotypes of S. cernua have also proven to 
be genetically isolated from S. magnicamporum, at least 
in the small sample available for study. Four plants of 
S. magnicamporum from two localities in Illinois (Greene 
and Lake counties) were crossed with three plants of JS. 
cernua, two of the old field ecotype from two localities 
(Pope County, [linois and Fountain County, Indiana) 
and one of the sand prairie ecotype (Kankakee County, 
Illinois). A total of twenty crosses were made using S. 
magnicamporum as the pistillate parent (because of the 
apogamous nature of S§. cernua) and flowers of several 
ages. Absolutely no seed was obtained from these crosses. 
It should be noted, however, that because of differences 
in period of anthesis, the pollen from the sand prairie 
ecotype of 8S. ceynua was stored for two weeks before use. 
It is clear that this apparent isolation does, in fact, 
occur. It is indicated by the situation in a region of dune 
and swale topography along the Lake Michigan shore 
in Lake County, Illinois. Here S. cernua (sand prairie 
ecotype) occurs by the hundreds in low sand prairie 
swales. Infrequent plants of S. magnicamporum are scat- 
tered on the xeric ridges. I have never found an inter- 
mediate plant in the field, despite intensive search, and 
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