126 PITTONIA. 
The species here to be discussed have already been named, 
at least in part, under two other genera outside of Sisym- 
brium ; Nuttall having referred them to Nasturtium in the 
beginning of their history, and Marcus Jones having pro- 
posed for them a place in Erysimum. This idea may have 
been an original one in the mind of Mr. Jones; but Hooker 
and Arnott very long ago made a like suggestion. 
In mode of growth there is nothing about this type to 
suggest Erysimum as we have understood that genus; noris 
there a trace of that peculiar forked and appressed pubescence 
found in every species of Erysimum and Cheiranthus. "The 
pods of Erysimum are either sharply four-angled, or else at 
least the valves have a strong midnerve, But in the things 
we are dealing with the pods are terete and without a mid- 
nerve, as far as I have been able to discover. On each of 
these points they to me seem far indeed from that group to 
which Mr. Jones would refer them. 
My own view is, that we have here one of the most pro- 
nounced among American genera of crucifers; and that 
there is no intimate relation between them and any of those 
diverse types which have made up the conventional Sisym- 
brium ; that they are not at all allied to that exceedingly 
natural and well-defined group, Cheiranthus and Erysimum; 
that, as a genus strongly demanding recognition, ScH@NO- 
CRAMBE will find its proper place somewhere between Thely- 
podium and Stanleya. 
It is, if I mistake not, an altogether unique type of crucifer® 
in the possession of long rambling branching horizontal 
roots or rootstocks which send up, at intervals, slender reedy 
shoots without trace of radical leaves. With the exception 
of one or two species of Stanleya, we have in North America 
almost no such perennial crucifers; our more enduring 
species—those not annual or biennial—becoming so through 
woody induration of the crown ‘or caudex, or by fleshy 
rhizomes or tuberous roots. Not even Stanleya is normally | 
perennial after the manner of SCHÆNOCRAMBE ; I have only 
S E ee C ME 
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