1 
192 
absent, and the calyx sometimes diminished to what seems a mere rim ; but in 
reality, in consequence of the ovary being inferior, the whole of the tube of 
the calyx as well as its rim remains adhering to the ovary, so that the calyx 
is not in fact materially diminished ; but Callitrichacese are absolutely achlamy- 
deous. Now I think we have only one instance among Polypetalous Exogens 
of an entire loss of both calyx and corolla, and that is in the genus Euphorbia ; 
but in that instance the non-developement of those organs is probably owing 
to the want of room for their formation in the contracted involucre within 
whose tube they are crowded ; but in CaUitrichaceae no pressure whatever is 
exercised, but the flow^ers are at liberty to develope to whatever extent their 
nature will admit of. For these reasons I consider that Callitrachaceae are to 
be looked upon as an absolutely achlamydeous order, and that being the case, 
it wdll necessarily take its place where I have now stationed it. It is quite 
true that no veiy striking affinity can be pointed out as yet between it and 
the other parts of the Achlamydeous group ; but neither can this be done if it 
is referred to Onagrales, and yet that alliance, compared with Achlamydosse, 
is very completely known. If it is said that its floating habit assimilates it 
with Myriophyllum in Haloragese, so does the same habit associate it with 
Podostemaceee. It is hardly worth pushing this discussion further, but other 
points worth notice will readily suggest themselves to any experienced 
botanist. 
Geography. Natives of still waters in Europe and North America. 
Properties. Unknown. 
GENUS. 
Callitriche, L. 
Group III. C^ubiferoi^ae* 
Essential Character. — Calyx tubular, often resembling a corolla. Ovary in most 
cases simple. Embryo never curved round albumen. 
Tliis may be considered as upon the whole,- the most highly developed 
form of Incompletee, the calyx being in all respects as perfect as that of Poly- 
petalse, and in some instances appendages at its orifice being produced which 
are analogous to petals, as in Thymelacese ; in those cases, however, the suc- 
culent nature of the appendages, their not withering away, the absence of spi- 
ral vessels from them, concur to refer them to abortions of the petaline rather 
than of the staminal series. It is here that we have one of the most direct tran- 
sitions to the Polypetalous sub class, for the relation of Daphnales to Rham- 
nales, of Proteales to Loranthacese, and of Lauracese to Myristicacese, are not 
to be questioned. The only cases in which this group can be confounded with 
any other, are in such plants as Scleranthaceae or Nyctaginacese ; but those 
have an embryo curved round mealy albumen, and besides are readily to be re- 
cognised after a little study. 
Alliance I. SANTALALES, 
Essential Character. — Calyx adherent to the sides of the ovary. Anthers opening 
by longitudinal fissures. 
