496 SECTIONAL TRANSACTIONS.— K. 



and of P. graminis and as confirmed by A. M. Brown (1935) in compound 

 pustules of P. helianthi in which a mixing of the pycnidial nectar was pre- 

 vented ; and (2) by the union of (+) pycnidiospore with a (— ) flexuous 

 hypha, or of a ( — ) pycnidiospore with a (+) flexuous hypha, as observed 

 by Craigie (1927 and 1933) in P. helianthi and by Buller (1938) in P. graminis. 

 Flexuous hyphae in pycnidia have been observed : by Craigie in Puccinia 

 helianthi and P. graminis ; by Pierson in Cronartium ribicola ; by Miss 

 Hunter in species of Melampsora, Milesia, Pucciniastrum, and Cronartium ; 

 and by Buller in twenty rust species belonging to the following genera : 

 Puccinia, Uromyces, Gymnoconia, Phragmidium and Gymnosporangium. 

 It seems likely that flexuous hyphae are present in the pycnidia of the rust 

 fungi in general. 



Saturday, August 20. 



Excursion to Wicken Fen. 



Sunday, August 21. 



Excursion to Forestry Commission Plantations in Thetford Forest. 



Monday, August 22. 



Joint Discussion with Department K* (Forestry) on The ecological 

 aspects of afforestation. (lo.o). (See under Department K*.) 



(concurrently with above session.) 



Sir Albert Seward, F.R.S., Mr. W. N. Edwards and Dr. J. B. Simp- 

 son. — The vegetation of the Inner Hebrides in the early Tertiary 

 period (lo.o). 



More than fifty years ago John Starkie Gardner obtained a large collection 

 of fossil plants from sedimentary beds near the base of the basaltic lava 

 flows at Ardtun Head in the island of Mull. He described several of the 

 plants but did not publish a complete account of the flora as a whole. In 

 the present communication the authors contribute a preliminary survey 

 both of the Mull flora, as represented by the Starkie Gardner collection in 

 the British Museum supplemented by specimens kindly lent by other 

 institutions, and of material from the island of Skye and a few other localities. 

 The results are expected to be published in the near future as an official 

 British Museum Catalogue. 



The present contribution includes : (i) an account of the flora based on 

 impressions, almost exclusively leaves ; and (ii) an account of pollen 

 investigations by Dr. J. B. Simpson. Special attention is drawn to con- 

 trasts in geographical distribution illustrated by comparison of recent and 

 extinct species of some of the genera represented in the Mull leaf-beds, e.g., 

 Onoclea, Amentotaxus, Sequoia, Cephalotaxus, Ginkgo, Cercidiphyllum, 

 Platanus, and several others. The examination of the pollen which is 

 abundant in the lignites of Mull and Ardnamurchan confirms the pre- 

 dominance of forms whose habitat is now Eastern Asia. This is evidenced 

 not only by the presence of genera such as Ginkgo and Bucklandia 



