﻿456 ON THE GENUS CROOMIA. 



are no medullary rays, and no trace of cambium-layer and liber. Not being prepared 

 to illustrate its anatomy at present, it may suffice to say that the woody layer of the 

 rhizoma appears as if composed of a series of such bundles as those in the leafy stem, 

 but completely and very irregularly confluent into a closed zone. 



The only endogenous stems I know of which exhibit a distinct pith are those of 

 Dioscorea. The rhizoma of Croomia in structure is not materially unlike the her- 

 baceous leafy stems of Dioscorea villosa, and the foliage and habit of Croomia are al- 

 together Dioscoreaceous. 



It is needless to enumerate the obvious points of diflerence between Croomia and 

 the Dioscoreacece, now that I can point to a different but allied group, hitherto mono- 

 typic and altogether peculiar, to which our present genus may doubtless be directly 

 referred ; namely, the JRocchiirghiacece, proposed as a natural order to contain the small 

 Eastern- Asian genus Roxhiirghia alone. As now augmented by another genus, it may 

 prefer a better claim to ordinal rank. 



I possess no specimens of Roxhurghia ; but a comparison with the published char- 

 acters, and with Wallich's figures of the fruit and seed of jR. viridiftora, leave no doubt 

 that Croomia and Roxhurghia are members of the same and a peculiar natural group. 

 The principal dififerences are in the configuration of the stamens, in the attachment 

 of the seeds, t&c, and are merely generic. The two genera may be contrasted in their 

 essential characters as follows : — 



1. E.OXBURGHIA. Sepala plurinervia, acuta vel acuminata. Filamenta basi mona- 

 delpha: antherse facie interiore connectivi maximi apice subulato-producti adnatse, 

 loculis angustis ex apice vacuo subulatis vel mucronatis. Semina ad chalazam rostel- 

 lata, ex Endl. " in placentis parietalibus ad basin valvularum plurima e funiculis elon- 

 gatis, apice in arillum stuposum solutis erecta." Embryo " albumine quadruple 

 bre\ior " (ex Kunth), subclavatus, " extremitate radiculari incrassata." (Endl.) — Suf- 

 frutices volubiles, Orientali-Asiatici, foliis plerisque oppositis seu verticillatis, floribus 

 sat magnis. 



2. Croomia. Sepala ovalia, obtusa, fere enervia. Stamina discreta : antherae breves, 

 filamento oblique introrsum impositae, connective nullo. Semina pauca, per funiculos 

 breviusculos copiose crinigeros apici placentae filiformis intervalvularis inserta, sus- 

 pensa. Embryo minutus, obovatus, extremitate cotyledonea incrassata. — Herba humilis 

 Americse Boreali-orientalis, caule erecto apice folioso, floribus parvis. 



Plate XXXI. Flowering plant of C^ooma joaiwj'/Zoj-a, of the natural size. Fig. 1. Peduncle and flower- 

 buds. 2. Diagram of the flower in transverse section. 3. Vertical section of a flower-bud. 4. Vertical 



