Menispermacea.] flora indica. 173 



they present ; and the mere fact of there being in some cases definite periods for the 

 formation and suppression of the liber, indicates the existence of functions that will 

 one day find expression as natural laws. In pursuance of Decaisne's investigations, 

 we would recommend the study of the anatomy of the internodes of various parts of 

 the stem, in relation to the development of flower-buds and leaf-buds on the parts 

 above them. 



The absence of annual rings of growth in wood many years old, indicates a more 

 general vitality in the stem, or, at least, a less definite boundary between the living 

 and dead wood ; in other words, a more generally diffused activity of the stem seems 

 necessary to the life of the plant than is usual amongst Exogens, whose inner layers 

 of wood are virtually inactive. The very frequently woody nature of the pith-cells, 

 which form long cylindrical rigid tubes with blunt square ends, placed above one 

 another, would also appear to be an adaptation of that part to some modification of 

 its nsual functions ; but for what special design, we have no idea. 



2. The question whether the structure of Menisperms approaches that of Endogens, 

 has been well answered by Decaisne in the negative ; but as there are still two opi- 

 nions on the subject, we shall view this point in another light from that excellent 

 author. If the Endogenous stem is regarded as an imperfect development of the 

 Exogenous, and if (as is perhaps the general opinion) an annual addition to a once- 

 formed deposit of pleurenchyma and parenchyma, etc., be considered typical of the 

 highest-developed Exogenous stem, then Menisperms may, inasmuch as they depart 

 from these characteristics, be considered to tend towards Endogens ; but if, on the 

 other hand, the Endogenous stem be considered as constructed upon a totally diffe- 

 rent type from the Exogenous, and that the terms high and low are not applicable to 

 them in any but general terms, we lose sight of any transition being indicated by 

 Menisperms from the Exogenous to the Endogenous type; for whereas they offer 

 all the peculiarities of the Exogen as contradistinguished from the Endogen, they 

 share none of the distinguishing characters of the latter. The mere r Jinblance 

 of a transverse section of a Menispermeous stem, with several rather irregularly de- 

 posited zones of wood, to an Endogen, argues nothing, for the structure of the bundles 

 thus compared is totally dissimilar, no less than their relations to one another; and 

 whatever casual resemblance transverse sections show in these cases (and upon which 

 so much stress is laid), a vertical section annuls. 



The fundamental facts, that the vascular system of Menisperms is double, that each 

 in many cases, and one in all, increases annually, that the wood-bundles are sepa- 

 rated by continuous narrow medullary rays, and that on a vertical section the wood- 

 zones are all seen traversing the stem in straight lines, and always parallel to one 

 another, are entirely opposed to the view which would consider the Menispermeous 

 stem as showing an approach to that typical of Endogens. 



3. The Exogenous Orders to which Menisperms may be supposed to betray an 

 affinity in the structure of their stems are mentioned above, but identity of structure 

 is hardly to be found between Menispermacea and any of them. The greatest n m- 

 blance exists perhaps in Myzodeyidron, an erect -growing Santalaceous plant, and the 

 horizontal rhizomes of some Balanopkorea, but upon these it would be superfluous 

 to dwell. Much stress has been laid upon the resemblance to Aristolochia and 

 Decaisne has exposed the mistaken views upon which this was founded, showing, in 

 the first place, that this is neither constant nor of importance; and in the second, 

 that the genus Arutolochia presents as many variations from a common type as 

 Afenisjjermacea do, and that these deviations are neither common to both Orders 

 nor analogous in each. 



In the present state of our knowledge, we cannot do better than quote Decaisne's 

 remarks, that "no special value can be attached to characters drawn from the organs 

 of nutrition," and that "all observations tend to prove (as MirbeJ has already said) 

 that the anatomieal structure of wood offers no sure guide to affinity." 



We have still a few words to add upon the individual pceuliaritu s of Menispermcon- 

 woods. With r u-d to any agreement in wood structure amongst tl nsclve% which 

 the plau^ erf this Order show, it is very vagm closely allied genera have often very 



