410 



NYMPH^ACE^. 



[Hypogynous Exogens. 



It seems, however, desirable to state, in this place, what the reasons are which have 

 led so many modern Botanists to place the Order in the class of Exogens. If the 

 rhizome of Nymphsea is examined it will be fomid to consist principally of cellular 

 tissue, with a very confused disti'ibution of fibrovascular bundles among it, not at all 

 like that of Exogens, but more resembling what occurs in succulent Endogens, Bijt, 

 according to Mu-bel's examination of the anatomy of the roots of Nuphar luteum, in the 

 Anrmles du Museum, vol. 16, pi. 20, the bundles of fibres are there placed in a con- 

 centric circle, the yomigest being outermost. Secondly, the leaves are those of Dico- 

 tyledons, and so is their convolute vernation, which is not known ni Monocotyledons, 

 together with then* insertion and distmct articulation with the stem. Tliirdly, the 

 flowers of Waterlilies have so great an analogy generally \vith Dicotyledons, and par- 

 ticularly with those of Magnohads, and their fi-uit with Poppyworts, that it is diffi- 

 cult to doubt theu' belonging to the same group. 



It is not possible to refuse assent to the importance of some, at least, of these con- 

 siderations ; but I do not think that they quite dispose of the question as to where, in a 

 Natural System, N;yTnph£ea and its allies are to be placed. To the foliage httle value can 

 be assigned, for it is sufficiently Hke that of Hydrocharis. Nor does the stinicture of 

 the root of Nuphar prove the stem to be an anomalous form of Exogens ; for the 

 cu'cle of fibrovascular bundles found there is the common character of the roots of 

 Endogens, as Schleiden first pomted out, and has no resemblance to that of Exogens. 

 The argument derived from internal structure is therefore more in favom' of Water- 

 lilies being Endogens than Exogens. The true ground for considering them Exo- 

 gens is certainly confined to the two-lobed embryo. It seems to have been forgotten 

 that when Brown and Brongniart proved Richard's cotyledon to be nothing more than 

 the amniotic sac, they did not also prove, as a necessary consequence, that the so-called 

 plumule of Richard was a dicotyledonous embryo. It may be monocotyledonous, 

 notwithstanding its vitellus. Certainly its two lobes are very hke those of Exogens ; 

 but I find that in NjTnphsea alba the lobes are not suddenly contracted at theii- base 

 like true cotyledons, (nor are they in Nelumbium,) and, moreover, that the plumula is, 

 in that plant, placed in an oblique direction \\A\h respect to the lobes ; so that, in fact, 

 the embryo of Nymphaea is much like a modification of such monocotyledonous embryos 

 as those of Aponogeton, Cjonodocea, and Posidonia. — See Ann. Sc. n. s. xi. t. 17. 

 Indeed, I perceive no reason why it should not be regarded as having one split 

 cotyledon, rather than two distinct ones. The principal mass of the nucleus in the 

 seeds of Orchids appears from the researches of Professor Lmk to be an analogous 

 case. In these plants the nucleus is a spheroidal cotyledon, from whose surface the 

 radicle and plumule respectively protrude. We have only to imagine it elevated on each 

 side, and we should have the two-lobed body of this Order. For the present, however, 

 I am not prepared to distui'b existing arrangements ; though I much suspect that it 

 will be done by some other Botanist. Indeed M. Ad. Brong- 

 niart has lately declared that the position of Waterhhes 

 appears to him very doubtful. — Enumeration xxv. De Can- 

 dolle assigns as a further reason for considering Waterhlies 

 to be Dicotyledons, that they are lactescent, a property not 

 known in Monocotyledons. But in this he is mistaken ; Lim- 

 nocharis, a genus belonging to Butomads is lactescent. 

 Finally, Mr. Hassal appeals to the condition of the pollen of 

 Watei'hUes, which he thinks proves them to be undoubted 

 Monocotyledons. The pollen gi'ain of Nymphaea is de- 

 scribed by this observer as being oval, hispid, with a fiu'- 

 row down one side, and emitting a smgle pollen tube, which 

 marks he regards as characteristic of Endogens. 



The germination of Nymphsea alba is not exactly either 

 exogenous or endogenous. The radicle is clearly endorhizal, 

 as in the latter ; but the cotyledons lengthen their bases to 

 allow the plumule to escape, just as m a.n acom ; and this is 

 perhaps one of the strongest arguments in favour of the lobes 

 of the embryo being really cotyledons. 



Supposing this Order to be exogenous and dicotyledonous, 

 its immediate affinity will be with Poppyworts, with some 

 genera of which it agrees in the very eompomid nature of 

 the fruit, from the apex of which the sessile stigmas radiate, 

 in the presence of narcotic principles and a milky secretion, 

 and m the great breadth of the placenta. Waterlilies Arc 

 also considered akin to Magnohads, with which they agi'ee 



Fig. CCLXXXVII. bis. 



Fig. CCLXXXVII. 6w.— Germination of NjTnphsea alba. 



