732 On the Natural Succession of the Dicotyledons. [ November, 
on which such separation was based is at least strongly suggested. 
The resemblance, above pointed out, which the Caryophyllacee 
bear to the Po/ygonacee illustrates this. In these orders the corolla 
and the ovary, two of the most reliable characters, are sufficiently 
distinct in typical genera to justify a separation, but when led by 
the stipules, swollen joints, leaves, habit, and other peculiarities 
that combine to make up their general appearance, to place them 
in juxtaposition and study them comparatively, we find that even 
these characters fail in certain genera, while the relationship indi- 
cated by the physiognomy is partially supported by more respect- 
able evidence. We have already seen that several members of the 
chickweed family are apetalous. On the other hand some genera 
of the Polygonacee may be regarded as at least functionally dichla- 
mydous, as in Chortzanthe, the one-flowered involucre closely 
imitating a calyx. And further, the capsule of several genera of 
the Caryophyllacee (Paronychia, Anychia, Scleranthus) is reduced 
to a one-seeded utricle anprogchiog the achenium of the buck- 
wheat family. 
While, therefore, the time has not yet arrived for the attempt 
to be made to trace out the line of genealogical descent of the 
Dicotyledons, it is evident that a complete re-adjustment of the 
orders, to a great extent independently of the present divisions, 
will have to be made and might soon be undertaken. 
The first dicotyledonous plants were in all probability apet- 
alous, and all authors agree in placing the Amentacee ( Fuliflores 
of Sachs) at the bottom of the scale. It is certainly not without 
` significance that the Casuwarinee, whose possible descent from the 
Guetacee (Ephedra) was referred to in the previous article, belong 
to this group. 
The origination and development of the corolla was doubtless 
by a process similar to that by which the calyx was formed. In 
_ both cases it was the advantage, however slight, which the plant 
derived from it that occasioned its progressive development into 
a protecting organ. In the Amentacee,as also in many Mono- 
_cotyle ( Cyperacee, Gramine@), these envelopes are very imperfect, 
-= often reduced to mere scales. Polypetalous plants (and doubtless 
2 apstalous also) may be of two kinds, according as the petals may 
Showa. to represent rudiments of a gamopetalous corolla in 
ocess of development, or only vestiges of one which they for- 
ssessed, The terms _ z Per and “ monopet- 
