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XXXIII. On the Embryos of Ende and their Germination. 
By BENJAMIN CLARKE, Esq., F.L.S. 
A^ 
Read June 16th, 1859. 
IT is now some years since L. C. Richard, in his original and very accurate work, the 
‘Analyse du Fruit *,' divided phanerogamous plants, with reference to their germina- 
tion, into Endorhizæ and Exorhize; but notwithstanding that exceptions to the exo- 
rhizal character as regards the secondary radicles have been repeatedly observed in 
exogenous plants, and its universality in the primary radicle doubted, yet in general 
works in which germination is referred to, this division is considered practicable, and the 
Endogens also are still regarded as being constantly endorhizal. 
In examining the germination of the Endogens, however, for the purpose of ascertain- 
ing the position of the first leaf of the plumule relatively to the cotyledon, the primary 
radicle proved, contrary to my expectation, to be perfectly exorhizal in the greater number 
of instances, and so obviously without any trace of a sheath (coleorhiza) in Zris, Alströ- 
meria, Smilacina, Butomus, Tamus, and Arum, as to place the fact beyond question. 
The secondary radicles in the Endogens, it is true, are usually, if not always, endorhizal, 
inasmuch as they protrude from beneath the cellular integument common to the primary 
radicle and young stem, although no sheath may be present; but this is a character also 
common to certain Exogens, as Menyanthes trifoliata, in which the secondary radicles 
and their branches not only protrude from beneath the surface, but have small sheaths at 
their bases; and some of the more remarkable instances of this kind have been described 
as occurring in the germination of Ranunculaceæ, Composite, and other families. The 
germination of Nuphar lutea also presents another remarkable instance in which the 
primary radicle is perfectly exorhizalt, but the secondary radicles above it are ms 
rhizal, the elongated sheaths remaining attached during the early stages of growth. 
(Pl. LXVIII. figs. 1, 2, & 3.) EE BER ! | 
_ Finding, therefore, the Endogens to be frequently exorhizal, as many of om og oppor- 
tunity afforded were germinated, and the probability appears to be that the primary or 
- true radicle is known to be endorhizal (with two additions afterwards noticed) only in 
and Graminaceæ. 'To these families should 
figured Zannichellia palustris as having 
& 
Marantacee, Commelynaceæ, Cyperaceæ, 
perhaps be added Naiadeæ, since Richard has ; 
all the appearance of an endorhizal germination ; bat whether they ge ji Pet 
be a question, because the embryos of some genera in their radicular po | e E 
materially from those in which the germination is exorhizal ; and al = e ti 
Zannichellia no trace of a sheath is perceptible in a longitudinal section, = 
* Démonstrations, ou Analyse du Fruit, 1808; H. A. Duval, Ed. ` SR 
en ing endorhizal, but as I have not had an opport ty 
+ The germination of Nymphæa alba has been referred to as being ESO d nie give it in 
of seeing it, this observation on Nuphar lutea was made with the greatest care ; ! 
x : AR wer s to be entirely an appearance. 
some degree the appearance of being endorhizal, but on examination it proves to be entirely TÅ 
VOL. XXII. 
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