Nov. 1894.] BOTANICAL SOCIETY OF EDINBURGH. 279 



and believe that the sporogenous tissue of to-day is a residue 

 which still performs the function to which the whole 

 primitive sporophyte was devoted, should appraise at a 

 fitting value all the developmental facts which lead up to 

 the culminating point of spore-formation. I can conceive 

 that in the future some of the most weighty comparative 

 evidence may be found in the early steps of differentiation 

 of the sporogenous tissue. 



I would, in the second place, draw your attention to the 

 greatly increased interest which will now attach to the 

 abnormal phenomena of apogamy and apospory. 



In entering upon the consideration of these abnor- 

 malities, Strasburger first discusses the cpiestion of the 

 maintenance of individuality of the chromosomes even in 

 the resting nucleus. He concludes, that though they "may 

 lose their morphological individuality, they do not lose 

 their physiological individuality"; and it is the main- 

 tenance of this individuality which determines on division 

 the breaking up of the chromatin into a definite number of 

 chromosomes. The reduction is due to the fusion into one 

 of two chromosomatic individuals. The doubling of the 

 number in fertilisation is due to the coalescence of two 

 equal sets of chromosomes from the two conjugating nuclei. 



You will clearly apprehend that if the difference in 

 nuclei in the alternating generations be such as has been 

 described, there must be an abnormal change in their 

 condition accompanying the phenomena of apogamy and 

 apospory. It is true that variations in number of chromo- 

 somes take place in somatic cells which have passed from 

 the embryonic condition ; but this will not suffice as a 

 general explanation of the changes in apogamy and 

 apospory, since these growths commonly arise from cells in 

 the embryonic state. It may be reasonably understood 

 that the nuclei of the apogamous bud may by some means 

 have acquired a double number of chromosomes, without 

 any ostensible sexual coalescence. In the aposporous 

 growths the nuclei will have undergone a reduction, and 

 since many of those growths appear quite independently 

 of the sporangia, we must conclude that other cells than 

 the spore-mother-cells are capable of undergoing a reduc- 

 tion of chromosomes. It is even to be noted that in many 



