(Vol. 8 
128 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
curious and is perhaps to be explained by chance dispersal far 
from the original area occupied by the species. 
Occurrence of the Species upon Calcareous Soils.—It is evident 
that many species of this genus occur upon calcareous soils. 
Pertinent data has been assembled in the hope of observing sig- 
nificant correlations between this habitat and previously ob- 
tained phylogenetic conclusions. The following species have 
been collected upon calcareous soil according to data preserved 
on herbarium sheets: L. lasiocarpa, L. Schaueriana, L. densi- 
flora, L. Engelmannii, L. ovalifolia, L. arctica var. Purshii, L. 
recurvata, L. gracilis var. sessilis, L. argyraea, L. Fendleri, and 
L. rectipes. A. Gattinger, in the ‘Flora of Tennessee, notes 
that L. Lescurii occurs only upon calcareous soils. Fernald 
(Rhodora 13: 233. 1911) says that L. arctica var. Purshii in 
Newfoundland is a typical calciphile, and Kurtz (Rev. Museo 
La Plata 5: 286. 1893) observes that L. mendocina grows in 
dry and especially calcareous habitats. Mr. E. J. Palmer has 
told the author that L. ovalifolia seems restricted to limestone 
regions. Dr. Aven Nelson says that he has collected L. conden- 
sata upon outcroppings of limestone. Certain other species may 
be suspected of being calciphiles, since the regions from which 
they are reported are known to be very largely calcareous. 
L. angustifolia and L. gracilis belong to this category. An exam- 
ination of this list of fifteen species shows a large number of 
primitive forms. Since the genus is believed to have originated 
in a region in which limestone is very frequent, this is not sur- 
prising. It is of considerable interest to note that primitive 
species in each of the three sections are calciphiles. Undoubt- 
edly, many species of the genus are not limited to calcareous 
soils and many more probably never occur on them. Definite 
data on this point is very meager. L. montana, L. diversifolia, 
and L. Garrettii are known to grow in granitic soils. It will be 
noticed that these are highly specialized species. Before draw- 
ing any conclusions it must be said that from such fragmentary 
data no more than tentative results can be expected, and since 
many cruciferous plants are partial to limestone regions this 
partiality does not necessarily imply close relationship. How- 
ever, it would seem that the immediate ancestors of Lesquerella 
were calciphytes. A bit of evidence in favor of a common origin 
