408 MR. B. CLARKE ON THE EMBRYOS OF ENDOGENS 
cumstances, as long as the cotyledon, but no trace of it is present before germination. It 
cannot be a rudimentary leaf, because it has no connexion with the base of the plumule, 
but only with the margins of the opening in the cotyledon. 
` Iridee.—The embryos of several species of Zris agree in their germination with those 
of Argcee and Liliaceæ; they are, however, remarkable for the cotyledon sending up a 
sheath surrounding the plumule, which sometimes becomes longer than the cotyledon — 
itself, and terminates by elongating internally between the plumule and cotyledon (fig. 26). — 
In other species of the same genus, this sheath exists only as membranous margins of the 
elongated opening in the cotyledon, which proves beyond doubt it is of the nature of 
stipules. | 
Amaryllidee.—The germination of Alströmeria aurantiaca agrees precisely with the 
species of Iris in the primary radicle being exorhizal, and the secondary endorhizal, or at 
least breaking through the cellular surface; but the stipulary process, as I have termed 
it, is wanting, which is a further proof of its real nature in Tris. i 
Digscoreacee.—The germination of Tamus communis agrees most with that of the 
Liliaceæ. The first leaf of the plumule alternates with the cotyledon, and not only is it 
exorhizal, but it is some time before any distinetion between the cotyledon and radicle is 
apparent. The opening for the emission of the plumule is horizontal, and a sheath, like 
that which forms in Asparagus, rises round the nascent plumule, and, as growth advances, 
becomes external to it instead of next the cotyledon, which gives it in some degree the 
appearance of à second cotyledon; it is, however, often bifid, and the young leaves, as well 
as those which are mature, have lateral stipules, which alone might be sufficient to explain 
its true character *. | 
With reference to the value of the characters, it may be observed that they will probably 
prove of some practical use in subdividing the Endogens; Graminaceæ, Zosterace@, ` 
Naiadeæ, and their allies forming a natural section, and containing, it may be antici- 
pated, all the truly endorhizal and macropodal hypogynous families; and, on the other 
hand, Aracee, Liliacee, Dioscoreaceæ, Trideæ, and their allies, in which these characters 
are wanting, are all otherwise in near affinity to each other. | 
Such a subdivision, however, would involve the placing of the Marantaceæ, Musaceé .— | 
and Amomee, and also the Orchideæ and Burmanniaceæ on account of their large 
radicle, m the endorhizal section, with which they have scarcely any connexion except 
the affinity between Orchidee and Triuridee ; but yet their epigynous character should 
not perhaps be regarded as excluding them, because of the truly epigynous character e 
the Hydrocharideæ. If, however, Von Martius is right in his comparison of Burmanni- 
ace@ with Hydrocharideæ, to which he refers them, another link of connexion between 
Orchidee and the hypogynous endorhizal families may be traced; and it may also deserve 
notice, that the embryo of Orchis Morio in germination becomes in shape much like that 
of a Ruppia, the young plumule also springing from the same part. The ovules of Bur- 
manmaceæ are orthotropal, and the distichous inflorescence of Burmannia dasyantha t 
* i 3 = ; ; 
å This stipulary DEM NE the ungerminated embryo of Dioscorea cordifolia, as figured by Ad. de Josse 
and 15 represented as bifid. (Ann. des Sciences Nat, gme Série, xi. Bot. pl. 17. fig. 13.) 
t Nov. Gen. et Sp. Plant. Brasil. tom. i. tab. 5. fig." 
