.. in which the petals are united, and others where they are quite abortive; 
XXX PREFACE. 
corolla being of one piece, and not of distinct petals, which last is point- | 
ed out by names, Epipetale, &c. The other parts of the names, epi a 
(upon), peri (around), and hypo (under), need no farther explanation. 
While engaged in the study of plants alone, it is obviously of little 
consequence whether we begin, as Jussieu did, by the Acotyledones, or 
by the Dicotyledones; but if we view botany as a science that treats of 
only one of the great kingdoms of nature, and wish to introduce it into 
a Systema Nature, we must bring those portions of each most closely 
together which are most nearly linked. So that if we commence by - 
Zoology, we must first describe the Mammalia, and end by those of a 
simpler structure, and then take up the most allied of the Acotyledones, 
and follow the steps of Jussieu. But if we describe vegetables in the 
first place, we must begin with the Dicotyledones, and finish with the 
Acotyledones. When, however, a Systema vegetabilium is contemplated 
without reference to animals, it may perhaps smooth the way to the stu- 
dent if it commence by those more obvious, and, though of more com- 
plex formation, yet more simple to be comprehended. On this account - 
De Candolle has reversed the arrangement of Jussieu. 
_ We have said that in some respect the system of Jussieu is artificial, — 
and therefore his orders need not necessarily follow each other precisely 
as he has left them. De Candolle accordingly divides the Dicotyledones 
into Thalamiflore, or those whose petals are distinct and hypogynous ; 
Calyciflore, having the petals either distinet or united, but always in 
serted on the calyx; Corolliffore, with the petals united, and hypogy- 
nous, and bearing the stamens ; and Monochlamydee, with a simple pe- 
rianth or perigonium. Moreover, he derives his characters for all these 
united, not from the cotyledones, but from the structure of the stem, 
and terms them Exogene ; and in a similar way he calls Monocotyle- 
dones by the name of Endogense, with this alteration, that he supposes | 
the ferns and allied plants, which we have termed Ductulose, to have - 
the same structure of a stem as the Monocotyledones, and therefore di- 
vides the Endogenz into Phanerogame and Cryptogame. The other | 
Acotyledones named by him Cellulares, from their entire homogeneity 
of cellular tissue, conclude the system. 
We ourselves shall follow pretty closely that given by De Candolle,” 
because, from his publishing a book containing all the known species ar 
ranged according to it, it is almost the only one that can be of use to a 
student ofspecies. But while we do so, we shall subdivide his groups 
in the manner recommended by Jussieu: this will assist the inexpe- 
rienced botanist in referring to the orders, but must not be implicitly | 
trusted to; thus among the orders with several petals, examples occur 
in some orders with hypogynous stamens, genera may occasionally be 
