TRANSACTIONS OF SECTION K. 857 



5. On the ProthaUus and Embryo of Dansea. By G. Brebner. 



Mr. Bretner gave an account of the prothallus and sexual organs of Dansea 

 simplicifolia, Rudge, as the result of investigations made on some material fiom 

 the Botanic Gardens in British Guiana. He pointed out that there is a close 

 similarity between DoncBa and the ether two genera of the Marattiacece, An- 

 giopteris and Marattia, of which the prothallus has been previously described. 

 An interesting fact was noted as regards the prothallus rhizoids, which possess a 

 distinctly septate structure, and so far resemble a moss protonema. Possibly 

 'imilar septate rhizoids may be found in the other marattiaceous genera. The 

 development of the antheridia oi Danaa agrees in the main with that in Marattia 

 and Angiopteris : the material did not allow of any developmental study of the 

 archegonia. The concentric bundle of the primary embryonic stem shows an 

 endodermal layer. On the whole the author found in Dancea a complete agree- 

 ment, in all essential features, with Avgiopteris and Marattia, as regards prothallus, 

 reproductive organs, and embryo development. 



6. On Cross and Self Fertilisation, with sjjecial reference to 

 Pollen Prepotency. By J. C. Willis. 



The time has passed for regarding self-fertilisation as being always necessarily 

 harmful in itself, and it is now recognised as a regular feature in the life-history of 

 many plants. There exist many cases of plants in which both self and cross polli- 

 nation occur nearly, or quite, simultaneously, and it is very desirable to know what 

 happens in these cases. Darwin's experiments render it probable that prepotency 

 of foreign pollen is usual. The author's experiments have been devoted to a study 

 of the relative chemical attraction of ' own ' and ' foreign ' pollen by the same 

 stigma (chiefly in gelatine and agar cultures), and have given negative results. It 

 seems probable, putting together all the various known facts, that prepotency, 

 where it occurs, is due to actions set up after the pollen tubes have entered the 

 stig-ma, these actions tending to favour the growth of the ' foreign ' pollen-tubes, 

 and to check that of the ' own ' pollen. 



