NortH AMERICAN EQUISETUM 67 
laevigatum, it will be remembered that, unfortunately, 
Engelmann had gone to his reward long before such 
misplacement was perpetrated by Eaton and Farwell. 
It was certainly not the older botanists who made the 
misplacement nor the present writer. 
In Asa Gray’s ‘“‘ Manual of the Botany of the Northern 
United States,” Fifth Edition, 1868, (the first manual 
ever used by the writer), E. laevigatum Braun is traced 
out as follows: “Evergreen or perennial-stemmed, 
surviving the winter, mostly rough (the cuticle abound- 
ing in silex): fruiting in summer; spikes tipped with a 
rigid little point. (Stomata in regular rows, in our 
species on each side of the groove.) Stems tall and stout 
(114°-4° or even 6° high), simple or casually branched, 
evenly many-(15—40-) grooved: sheaths appressed.... 
Smooth or minutely roughish with minute tubercles; 
sheaths elongated,’’ etc. 
This is again a fairly accurate diagnosis except that 
the sheaths are not appressed when compared with £. 
praealtum, for example. 
Practically the same treatment was given in the 6th 
edition of Gray’s Manual, in Underwood’s “Our Native 
Ferns,” in Britton and Brown’s Illustrated Flora, in 
Small’s Flora of the Southern United States, in Piper 
and Beattie’s Flora of Southeastern Washington and 
Adjacent Idaho, and by various other authors. In fact, 
all of these authors seem to have understood Engel- 
mann’s treatment alike, and it is, therefore, quite in- 
teresting to read Farwell’s insistence on following 
“descriptions” when he utterly fails to do so himself. 
Equisetum does not fall into two clearly defined 
natural groups. It is out of the question to establish a 
genus Hippochaete. The distinctions are not sharp 
enough for two sub-genera or sections since there are 
always transitional species. One can make a number of 
subsections but these are too closely allied, according to 
