72 . Mr. Roscos on. Artificial and Natural 
among many others, the natural order of asperifolize ; as that of 
Pentandria digynia does of the umbellifere. The difficulties 
under which Jussieu labours now become apparent. He has in- 
deed formed the vegetable kingdom into fifteen classes; under 
which heads he has arranged one hundred tribes or orders, each 
consisting of various families of plants supposed to be allied to 
each other; but when we ask for the distinctions of these orders, 
or, in other words, by what peculiarities they are to be recog- 
nised, and in what terms they are to be described, we find only 
a series of appellations, mostly derived from some particular 
genus of plants which is supposed sufliciently predominant to 
give a name to the order, and which order includes certain other 
genera which appear to be related to it*. H, however, we are 
dissatisfied with this mode of distinction, as affording us no de- 
terminate idea, nor giving us any clue to discover how such 
order is formed, we can only have recourse to a comparison of 
the descriptions placed at the head of each of the orders of which 
each class is composed. ‘That the Jasmine: may form a part of 
the same natural class as the Gentiane, although their relation be 
not very apparent, may be admitted ; because they equally ger- 
minate from two cotyledons, and have each a monopetalous 
corolla, situated beneath the germen: but when we ask why. 
these genera. are not also of the same order, we must seek for an 
auswer in the description prefixed to each order in the body of 
the work ; until by a careful perusal and comparison of these 
descriptions, which in many respects agree, we are at length 
enabled to determine in what the difference between a Jasmine 
and a Gentian, a Laurus or an Atriplex, | really consists, In this 
* Thus th e4th order of the 8th class is denominated Jasminece, and inis the Bat 
Maytenus—Nyetanther—Lilae—Hebe— Frasinus—Chionanthus—Olea—Philyrea— Mo- 
gorium—Jasminum and Ligustrum, 
secondary 
