128 PITTONIA. 
Plant of more southerly range than the last, oceurring in 
Utah and Nevada. The best specimen seen is in the Na 
tional Herbarium, and was collected somewhere in Utah in 
1875 by Mr. L. F. Ward. Mr. Watson's n. 96 from the East 
Humboldt Mountains, described as having lower leaves run- 
cinately pinnatifid and the upper linear and entire, may 
belong here; though there is nothing of the runcinate about 
the leaves of other Nevadan specimens; and there are no 
entire leaves in the duplicate (?) of Mr. Watson's plant de- 
posited in the U. S. Herb., even the cauline or rameal being 
cut much after the manner of those of a Stanleya. 
9. S. PYGMJEA. Nasturtium pumilum, Nutt. Journ. Philad. 
Acad. vii. 12 (1834), not of St. Hilaire (1824). Sisymbrium 
pygmaum, Nutt. in T. & G. F}. i. 91 (1838). This is described 
as being a dwarf, with lyrately pinnatifid lower leaves, and 
herbage not, as in the type, devoid of pubescence. That noth- 
ing has been added to the knowledge of the plant since 
Nuttall's time should be no reason for suppressing the species. 
$9. ERyYsIMuM and CHEIRANTHUS. 
The genera of crucifere are exceedingly difficult to define 
in set terms. Hence what is always convenient is heré quite 
necessary, namely, that for the satisfactory arranging of spe- 
cies in generic groups, a certain very marked type shall be 
chosen, and the genus be allowed to at once illustrate and 
define itself; the species showing close affinity for the chosen 
- type, if they exist, being admitted and all others excluded 
from the genus; this to be done as decidedly when it hap- 
pens to leave a genus monotypic as u pon any other occasion. 
Only by just this kind of process was the illustrious Tourne- 
fort able to classify this important family of plants. And. 
that his classification of them was eminently successful and 
satisfactory is certain, especially as one compares it with the 
endeavors of Linnseus, most of whose genera of erucifere 
