52 MR. J. MIERS ON THE FAMILY OF TRIURIACEE. 
seen in Seiaphila, Hyalisma, and Soridium, and the figures he gives of it* quite corre- 
spond with the details now offered of the seminal nucleus in these genera. Prof. Lindley 
has long contended that these two families belong to a distinct class, which he calls Rhi- 
zanths or Rhizogens; but Mr. Griffith, in his able memoir above-quoted, wholly accords 
with Mr. Brown’s views on this subject, and states that these plants, though with inem- 
bryonal seeds, or with what he calls a homogeneous-embryo-form structure, may, without 
violating the rules of classification, be considered as aberrant forms of an imperfectly 
developed state of exogenous or endogenous organization. Thus, Mr. Brown has always 
considered the Rafflesiacee to be allied to the Aristolochiee, and Mr. Griffith contends 
that the Balanophoree should be placed near the Urticee. 
The considerations before stated naturally lead to the inquiry, if in such plants no em- 
bryo exist, using that term in its ordinary signification, how is their propagation effected 
by a seed with a simple nucleus of aggregated cells? According to the views of most 
modern physiologists, the earliest development of an embryo within the ovule is the forma- 
tion of a germinal vesicle (primordial utricle of Mirbel), generated by the action of the 
pollen-tube upon the embryonal sac, and the degree of perfection in the organization of 
the cotyledon, radicle, and plumula, is evidently proportioned to the function requisite to 
the future elaboration of the leaves, or a more or less complex stem; but in the case of 
leafless plants, the same amount of development would be useless for so simple an economy 
of structure. This is even seen in plants of a very high degree of floral development, as 
in Cuscuta, for instance, where the embryo of its seeds is altogether deficient (apparently) 
of the usual requisites of cotyledons, radicle, and plumule f, as it consists of a simple 
spiral thread, not germinating in the usual manner from two fixed points, but from which 
pullulating vesicles are produced, indifferently from any point of its surface, thus proving 
that the organization of the embryo bears an evident relation to the economy of the future 
plant. The Orobanchee also present a very small undivided embryo, and the Monotro- 
pee have a minute nucleus, in which neither cotyledon nor radicle is perceptible; and this 
is included in a reticulated arillus, as in Burmanniacee. Another instance, still more 
striking, oceurs in Cactee, where in the leaf-bearing genera the cotyledons are fully deve- 
loped in the embryo, while in the leafless species the embryo is solid and undivided. In 
the same manner it is probable that in the Burmanniacee, Balanophoree, Triuriacee, &c., 
tha inembryonal nuclei, consisting of a series of germinating cells or cytoblasts, pullulate 
ak certain points, and thus perform all the requisite purposes of reproducing their very 
simple forms of structure, in a somewhat analogous way to that in which the ordinary. 
embryo effects the more complex organization of vascular fibres and elaborate tissues in 
the higher orders of Phænogamous plants, 
If we admit the existence of’ an organ, thus endowed with the function, but wanting 
the usual structure of the embryo, it should hold some adequate designation, and for this 
the term Protoblastus does not seem inappropriate, as it effects the same purpose as the 
— or plumula f. The word used by Mr. Griffith for this organ, * homogeneous 
embryo, would require that the ordinary embryo, in contradistinction, be called hetero- 
* Trans. Linn. Soc. vol. xx. pl. 8. fig. 9-14. 
: : T Lindley, Introd. to Bot. p. 217. 
1 Ina similar sense, Richard has applied the term blastus to the s: s 
plumula of the seed in Gramineæ. 
