234 Address by the President. [Sess. 



of the Phanerogams or flowering-plants, and it is likely that it 

 is to these plants the majority of you will turn. In doing so 

 you should carry on the study of them in a systematic manner, 

 taking up the various orders in succession, and thus mastering 

 their distinctive differences. As a guide to the localities where 

 the various specimens may be found, you would find Sonntag's 

 * Pocket Flora of Edinburgh ' useful. 



In naming the various books which I have done, I do not 

 at all mean that they are the only ones in the different sub- 

 jects, but only that I think you would find these sufficient for 

 your purpose. 



It may be that some of you would wish to apply yourselves 

 to the more recondite subjects of study : if so, you will find a 

 most interesting one in the fertilisation of plants. You can 

 study the changes which take place in the sperm-cell and the 

 egg-cell respectively, before the final coalescence of the two. 

 So far as has been established, there is in each of these cells 

 (sperm-cell and egg-cell) a definite number of what are called 

 chromosomes for each plant, and also for each animal. If, 

 then, these cells united without any previous change, there 

 would be a number of chromosomes in the daughter-cell re- 

 sulting from this coalescence, double those in the original cells. 

 This is, however, provided against in a most remarkable 

 manner. In each of the sperm- cells and egg-cells preliminary 

 divisions — called maturation divisions — take place, by which 

 the original number of chromosomes in each is reduced by 

 one-half, so that when coalescence actually takes place there is 

 in the daughter-cell the definite number of chromosomes ap- 

 propriate to the particular plant or animal. Here, then, is a 

 study fitted for the highest powers of observation and the best 

 glasses of your microscopes. A writer on this subject says : — 



"We thus know now what 'fertilisation' is. Through the labours of 

 the last decade the veil has been torn from a mystery of nature which for 

 thousands of years confronted humanity as unapproachable ; a riddle has 

 been solved for the solution of which a few centuries ago man did not 

 even dare to hope. Not a few have taken part in these labours." 



Some of you may wish to take a part also in carrying on 

 such labours, — there is ample scope in the field, — and to those 

 who do I wish all success. 



In your study of Nature I would, however, not wish that 



