1904-1905-] Address by the President. 233 



life, and here, perhaps better than in any other division, you 

 can study the processes of fertilisation and reproduction. Here 

 you have reproduction by means of fission, by conjugation, and 

 by spores. As instances of the first naode, there are the genus 

 Chroococcus, which consists of isolated rounded cells enveloped 

 by a thin wall of a blue-green colour ; and the genus Nostoc, 

 which forms a chain of cells. As an instance of reproduction 

 by conjugation, there is the genus Spirogyra, in which two 

 filaments come together, when the contents of some of the 

 cells of one of the filaments pass into cells of another fila- 

 ment and coalesce with the contents of these cells ; and not 

 only so, but sometimes the contents of the cell of a filament 

 pass into a neighbouring cell of the same filament. As 

 instances of reproduction by spores (swarm-spores), you have 

 the genera Ulothrix and CEdogonium, but in these it may be 

 mentioned there is also sexual reproduction. You will find 

 another very peculiar form of sexual reproduction in the genus 

 Vaucheria. These are, speaking generally, terrestrial and 

 fresh -water algae, but, as you are all aware, there are numer- 

 ous families of marine alg^ which form interesting objects of 

 study. The following books treat of these : — 



' A Treatise on the British Fresh-Water Algae,' West. 

 ' British Seaweeds,' Gatty (Mrs Alfred). 



(3) Bryophyta and PteridopTiyta. — These include the liver- 

 worts and mosses and the vascular cryptogams, and they form 

 an excellent division for study. You can trace the gradual 

 development of the vascular system from what appears to be 

 its beginning in special rhizoids of some of the liverworts to its 

 beautiful form in the bracken {Pteris aquilina). In the vascular 

 cryptogams, and especially in the ferns, you can trace very 

 clearly that form of reproduction called alternation of genera- 

 tion. You can sow the spores of the fern, and thus obtain the 

 prothallus on which the antheridia and archegonia arise, and 

 from the fertilised archegonium of which the young fern plant 

 grows. In this study the following books will be of use : — 



' Handbook of British Hepaticae,' Cooke. 



' The Student's Handbook of British Mosses,' Dixon and Jamieson. 



' Flowerless Plants,' Scott. 



(4) Phanerogams. — The foregoing remarks apply only to 

 the Cryptogams ; there is, in addition, the great sub-kingdom 



