147 



species stand isolated from all others by broad characters of differ- 

 ence which cannot well be supposed passable at a leap. The Linnsea 

 and the Adoxa are examples of this among our indigenous plants. 



We have still to inquire about direct facts towards establishing the 

 transition from one species into another. This will be a difficult sub- 

 ject to treat, because the very definition of the term " species," as 

 usually given, involves an assumption of non-transition ; so that any 

 case of real transition — supposing such a case to be adduced — would 

 be set down simply as evidence to disprove the duality of the species. 

 I must reserve this inquiry for another communication, lest it should 

 extend the present paper to a length incompatible with the limits of 

 the ' Phytologist.' Hewett C. Watson. 



Thames Ditton, April, 1845. 



A List of the Musci and Hepatic(B of Yorkshire. 



By Mr. Richard Sprdce, F.B.S. 



As I am on the point of setting out on a Botanical expedition to 

 the Pyrenees* and the south of Spain, and it is quite uncertain what 

 length of time may elapse ere my return, I venture to solicit your in- 

 sertion in 'The Phytologist' of the following list of Yorkshire Musci 

 and Hepaticse, which includes all the mosses that have been added to 

 the Flora of the county since the publication of Mr. Baines's work. 

 As a mere list oi Yorkshire species, it is as complete as I have it in 

 my power to make it, but the pressure of preparation for my intended 



* My object in visiting the Pyrenees is to collect and publish the flowering-plants, 

 Mosses, Hepatic® and Lichens of those mountains. I hope to have the Phanero- 

 gamic portion of the collection ready for sale in London by the end of autumn ; the 

 accurate determination of the species of the Cryptogamia will be a work of time, but 

 they will appear as early as possible after the flowers, and I propose to publish them 

 in the style of Drummond's ' Musci Americani.' Those of the readers of ' The 

 Phytologist' who have been in the habit of receiving specimens from me, will be able 

 to form an idea of the manner in which my Pyrenean collections will be got up, and 

 I much regret that the confining nature of my profession has prevented me from 

 cultivating so extensive a botanical correspondence as I could have wished. I may 

 add, however, that the specimens will be as perfect in every respect as it is possible to 

 procure and to render them. 



I contemplate, ere my return to England, to devote several months to the exami- 

 nation of Andalusia, and especially to the Sierra Nevada, with the same objects in 

 view. The vegetable productions of this rich but imperfectly known country are more 

 interesting than even those of the Pyrenees, and I have reason to anticipate the 

 discovery of many novelties. 



