1913-14.] BOTANICAL SOCIETY OF EDINBURGH 279 



special circumstance. Just as many species hold their own 

 in temperate regions only through association with cultivated 

 crops., so there are species in alpine and desert areas which 

 depend on such adventitious factors as the occasional visit 

 of a flock of sheep. I am sure that Circaeaster follows the 

 shepherd. It is likely, in my opinion, that Plumbagella 

 does the same. 



In the Central Asiatic Highlands the flocks during the 

 short summer make a long excursion up the valleys into the 

 higher altitudes, advancing by slow stages to a high eleva- 

 tion (even to 15,000-16,000 feet), and returning by similar 

 stages under the pressure of the advancing autumn. These 

 stages are performed by the same flock year after year, and 

 certain definite spots in the long chain are used, generation 

 after generation, as halting-places for a few days. These areas 

 are often clearances in dense jungle such as rhododendron 

 forest, and have sometimes a very characteristic vegetation. 

 The majority of the species are invaders from not distant 

 meadows and slopes, but a few are wanderers who have 

 had a long and precarious " trek " from an entirely different 

 clime — for example, a journey from the exposed and bare 

 Tibetan plateau to the dense forest of a Sikkim valley. 

 Circaeaster and Plumbagella are wanderers of this type, 

 and should be distinguished from the regular frequenters 

 of the sheep-tracks, such as certain Polygonaceae and 

 Chenopodiaceae typified by Polygonum ftlicaule, Wall., 

 Polygonum perpusillum, Hook. 1, Microgynaecium tibeti- 

 cinn, Hook. f. — which may be said to compose a definite 

 formation comparable to the Lagerpflanzen of the Swiss 

 Alps. 



A Tuberous Senecio from China. 

 By W. W. Smith. M.A. 



(Read 9th April 1914.) 



Senecio tuberivagus, W. W. Sm. Sp. nov. 



Species ex affinitate Senecionis farfaraefolii, Maxim, et 

 S. dahurici, Schultz-Bip. ; ob stolones subterraneos prae- 

 longos tuberibus terminates conspicua : praeterea foliis 

 floribusque discrepat. 



