330 JOUENAL OF THE BOYAL HOKTICULTUEAL SOCIETY. 



Climhing Plants. — The methods of climbing are numerous, but the 

 only ones that need be selected in illustration of mimetism are the 

 following : — 



The tendril of a Pea is readily seen to be a metamorphosed leaf ; 

 several of the leaflets may still remain perfect, while the rest are repre- 

 sented by their midribs alone, now much elongated and highly sensitive to 

 touch, so that they coil round anything they can grasp. 



If this be compared with a much branching tendril of a Vine a strong 

 similarity will be seen, but this latter is a metamorphosed flowering 

 branch and not a foliar organ at all, though it climbs in a similar way to 

 the tendril of a Pea. 



The tendril of Bryony is also foliar in its origin, but consists of a 

 single thread, which, as soon as the apex has caught anything, coils up 

 into a corkscrew-like structure, but having some of the coils turning in 

 one direction, the remainder, about an equal number, turning in the opposite 

 direction. 



In the Passion-flower the long slender tendril represents a flowering 

 branch, but it is in form and behaviour precisely the same as in the 

 Bryony. 



Ascidiform Type. — Perhaps no better illustration of plant mimicry 

 could be given than that between the pitcher of Cephalotus follicularis 

 and that of the many species of Ncpenthca. These two genera 

 represent two totally distinct families, and imply long and now lost 

 ancestries. The general appearance of their mimetic pitchers is precisely 

 the same in both. There is a similar lid," a pitcher of the same shape, 

 with an inrolled margin, glands being sunk into the surface of the lining 

 of the pitcher, which externally carries a fringed guide from bottom to 

 top. Yet, while the pitcher of Cephalotus is a metamorphosed leaf-blade, 

 that of Nepenthes is developed out of a water-gland, situated at the apex 

 of the blade, this latter taking no part in its formation whatever. 



Such complete case of mimicry as this is quite as astounding as any 

 between two kinds of insects, or between the " kangaroo mouse " and the 

 genus Mus. 



Conclusion as to Mimetic Vegetative Organs. — The above-mentioned 

 selection of cases is but a sample of what may be regarded as a general 

 principle in nature, which is, that since the living protoplasm is of one 

 and the same kind in all beings, as far as we know, where a certain 

 feature is evolved, a similar one may be expected under similar conditions, 

 and a mimetic organ is the result : that is, so far as the conditions of the 

 structure will allow. Thus the kangaroo mouse mimics a true mouse, but 

 retains its pouch and insectivorous teeth ; so a linear dicotyledonous leaf 

 (as of Lathyrus Nissolia) resembles the monocotyledonous grass-leaf, but 

 retains its branching venation. 



Floral Mimicry. — It is not at all uncommon to find one flower 

 imitating another of a quite different family. Thus, bracts are often 

 white or coloured other than green, and, so to say, answer for and do 

 duty as a corolla, as in Poinsettia, Euphorbia, and some umbelliferous 

 plants, as Astrantia, and in the " Everlastings " among Compositce. But 

 the imitation may be much more exact, and indeed so close as easily to 

 deceive the unwary. Thus some species of Cornus have four white bracts 



