SECTIONAL TRANSACTIONS.— K. 423 



Apart from the typically African elements, the most interesting feature of 

 the alpine zone is the presence of so many representatives of temperate 

 genera, as, for instance, species of Ranunculus, Arabis, Subularia, Cardamine, 

 Limosella, Sibthorpia, Luzula, Anthoxanthum, Deschampsia and Koeleria ; 

 the species may, indeed, be identical with those found in this country. It 

 appears probable that these are relics of a former more extensive temperate 

 flora, and their isolated presence in the alpine zone of the African mountains 

 can probably best be interpreted from a study of the climatic history of 

 these regions. 



Tuesday, September 15. 



Dr. M. Rosenberg. — Algal cultures (10.30). 



A survey of methods for algal cultures is given. The various factors, 

 such as chemicals, light and temperature, are discussed and their importance 

 demonstrated. 



The chief problems which have been approached with the help of 

 culture methods are outlined ; and examples are given chiefly of results 

 concerned with ecological and morphological investigations. In several 

 cases it has been possible to correlate changes in external conditions with 

 corresponding morphological or physiological changes (division rate). 



Culture methods, especially among the Desmids, open a wide field for 

 investigations, owing to the variations which occur in this group. 



In the genus Xanthidium, for instance, it has been possible to show 

 that two morphologically distinct types — so far considered as two species — 

 really are varieties of one species only, brought about by changes in the 

 external conditions. 



Mention of results by various authors working on these lines is also 

 made. 



Miss M. Reese.— A study of the microflora of two Cardiganshire rivers and 

 the effect of local lead mines on their algal population (11.0). 



A short history of the lead mines followed by an account of the pollution 



they cause. ••»»«. 



A description of the physical features of the rivers Rheidol and Mehndwr, 

 and an account of the collection of the microflora, its periodicity, and the 

 relation of the plants to floods. 



Prof. J. Doyle. — Development in Sequoia (11.30). 



Fertilisation and pro-embryo formation are described for Sequoia gigantea. 

 The gametophytes resemble those of Sequoia sempervirens closely, but the 

 pro-embryo, although showing variations in the later stages, is essentially 

 Cupressinean in type. 



Wall formation at the first post-fertilisation division is verified for Sequoia 

 sempervirens. Subsequent pro-embryo development is clarified. Among 

 other points of interest, it does not fill the archegonium when young. 



Prof. T. M. Harris. — The fossil horsetails (Equisetites) (12.0). 



Some Mesozoic horsetails are briefly described ; most of their features 

 being in obvious agreement with those of Equisetum. Their vascular 



