356 FLORA AMERICJE BOREALI-ORIENTALIS. 
tant views which they in some instances develope. In the larger 
families we have also frequently a general conspectus of the tribes and 
genera. 
Each genus has, after the short Latin diagnostic character and 
synonymy and Anglo-American name, a detailed English descriptive 
character with the etymology of the name, geographical distribution, 
and occasional notes on properties, affinities, and morphology, wherever, 
from their exceptional character, or from our little acquaintance with 
other genera, they could not be given generally under the natural order 
to which the genus in question belongs. And here we would advert to 
the great additional value the character and descriptions derive from 
the able assistance afforded by the botanical knowledge of the artist 
who made the drawings, to the botanist who compiled them from 
the examination of the specimens; thus establishing a double safe- 
guard against the perpetuation of those errors which, originating in 
ignorance, carelessness, or even errors of the copyist or of the press, 
have been transferred from work to work, until at length some one, 
finding that a plant does not agree with its received generic character, 
founds a new genus on points really common to all the species of the 
old one. We need only refer to such instances as the ovary of Vibur- 
num, the glands of Sesamum, the estivation of Annonacee, &c 
These Annonacee are the only instance in which we have detected a 
partial oversight of the kind in the North American ‘Genera.’ It is 
stated, vol. i. p. 65, that ** the Order very closely accords. . . with Mag- 
noliacee, from which the valvate xstivation and the ruminate albumen 
essentially distinguish it,” and in the ordinal character @stivatione val- 
vatd is printed in italics as a most important circumstance. We find, 
however, in the genus Asimina, Plate 26,* the zestivation' correctly 
represented as it is described, p. 67, “rather imbricated than truly 
valvate." It is, in fact, more or less imbricated in nearly the whole, if 
not in all true species of Uvaria, Unona, Guatteria, Duguetia, and some 
others—that is, in at least half the order —although universally de- 
scribed as valvate in all ordinal characters of Annonacee known to us. In 
many instances the overlapping of the three petals of each series is as 
evident as in many Magnoliacez. The real positive distinction between 
the orders is, so far as at present known, confined to the form of the 
albumen; whilst the texture of the petals gites to each order a peculiar 
* Plates 22 to 27 are in our copy numbered, by mistake, 27 and 22 to 26. 
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