Page:Journal of botany, British and foreign, Volume 9 (1871).djvu/302

 278 PROCEE'DINGS OF SOCIETUiS.

such a general habit iu leguminous and composite plants is familiar to every one. What have been hitherto spoken of as jnimetic plants are simply cnses where a plant belonging to one family puts on the habit characteristic of another. This is entirely different from mimicry among animals, inasmuch as the resembling plants are hardly ever found with those they resemble, but more usually in widely different regions. Mutisia speciosa, from Western South America, a Composite, has a scan- dent leguminous habit, and closely agrees in its foliage with Lntliyras marltimiis of the European shores (although that plant is not strictly speaking scandrnt). In the same way three different genera of Ferns have species (found in distant parts of the world) indistinguishable in a barren state. The term Mimicry seems objectionable in these cases, and I pro- pose Pseudomoi'i^hism as a substitute. As to the cause of the pheno- menon, I can only suggest that the influence of similar external circum- stances moulds plants into the similar form most advantageous to them. An illustration is aft'orded by the closely resembling bud scales which are found in widely separated Natural Orders of deciduous ti'ces as modifica- tions of stipules. I do not, however, think that the moulding influence need always be the same. I believe that diflerent external conditions may produce the same result ; in this respect they may be called analogous. For example, several identical plants are found on the seashore, and also on mountains. The reason is, I believe, that they are equally able to tole- rate the effect of soda salts and also of mountain climate; the tolerance of either unfavourable condition gives them the advantaii,e over less elastici- cally constituted plants, and the two are therefore analogous in their effect,

Professor Dickson remarked that instances of so-called mimicry were

by no means uncommon amongst plants. Comparing Eitphorbiacere with CactncerB and Stapdia, it was often practically impossible to distinguisii them without seeing their flowers. In these cases similar physical condi- tions appear to have produced the similarity. Mr. Carruthers said that

though not wholly agreeing with the views of Professor Thiselton Dyer, some facts occurred to his mind which rather sustained those views. The vegetation which bordered fresh- water streams throughout the world all conformed, more or less, in certain characteristics of foliage to the willow type ; this was true even of Australian Myrtaceous plants. With regard to Mutisia, he might say that he believed that from the suborder of which it was the type alone, the habit of alnr.ost all the principal Orders of flowering plants might be represented. He fully bore out the statements as to Ferns, and he pointed out that the wliole subject constituted one of

the special difficulties of fossil botany. Professor Balfour could confirm

the remarks of the last speaker as to the important bearing of this sub- ject upon fossil botany. The speculations as to the effect of maritime conditions upon plants were particularly interesting. It was by no means easy to give a satisfactory explanation of the occurrence of strand plants upon mountains. Plantago muritiiiia might be added to those already mentioned. Anneria maritima did not occur at the highest elevations. He had induced Professor Voelcker to analyse the ashes of this plant from its most inland situation in Scotland, ^q.\\ ]\IacDhui. They con- tained less soda and more potash than strand plants, and no iodine,

Avhich was present in the latter. Professor E. P. Wright admitted the

importance of the distinction which had been laid down. He supposed, however, that it would not be contended that such a thing as true

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