855 ^ 



Mr. Watson also exhibited examples of the true Viola flavicornis 

 of Smith in contrast with the V. canina of Linnaeus. They were 

 brought to the meeting in order to show, by fresh specimens, the dif- 

 ferences between the two (both in leaves and flowers), which were 

 very perceptible. Mr. W. remarked that small specimens of the or- 

 dinary V. canina had been erroneously figured in the ' Supplement to 

 'Enghsh Botany' for the V. flavicornis of Smith, and that Mr. Ba- 

 bingtou persisted in repeating the same error in the second edition 

 of his Manual (published that day), although he could not fail to 

 know now that the application of Smith's name "flavicornis" to the 

 plant of the 'Supplement' was an error on the part of Mr. Foi'ster. 



Mr. Watson also exhibited a variety of V. canina with smaller and 

 lighter coloured leaves than usual, and a smaller and pale purple or 

 pinkish corolla. He had found the original root several years ago, in 

 Surrey, and removed it into his garden, where it had flowered and 

 seeded year after year, all the seedling plants springing up around it, 

 still resembling the parent plant in size and colour, without a single 

 example of the ordinary V. canina appearing among them. He ad- 

 duced this fact in order to show the hereditary repetition of a variety 

 without instances of reversion to the normal characters of the species; 

 and that, too, in a character usually deemed so inconstant. Such a 

 repetition is frequently accepted for evidence of specific distinctness; 

 and yet cases like this prove its insufficiency. 



The secretary stated that he had Dr. Greville's authority to say 

 that he never collected Potentilla rupestris on Ben Lawers, and that 

 probably some mistake had been made through the similarity of name 

 with Potentilla alpestris. But that it is quite certain that the 

 exhibited specimen was P. rupestris, and it was rightly named on its 

 label, although (as now appears), inaccurately localized. 



A communication was read from Dr. Parkin "On the Cause of the 

 Failure of the Potato Crop," and of epidemic diseases in general, in- 

 dicating " that such maladies are not only the effects of volcanic 

 action, but also that the immediate cause of their production is the 

 generation of a gaseous substance in the internal reservoirs, and its 

 extrication into the surrounding atmosphere through the superincum- 

 bent strata ; and endeavouring to show that the pathological pheno- 

 mena presented by this vegetable pestilence were only reconcileable 

 on the supposition that a gaseous, extraneous and deleterious sub- 

 stance had been introduced into the interior of the plant." The paper 

 went into a train of reasoning to prove this conclusion to be a cor- 

 rect one, as indicated by the results of the application, in planting, 



