June 1891. J BOTANICAL SOCIETY OF EDINBURGH. 145 



to find the reduction of the sexual generation carried on in 

 Angiosperms as in Gymnosperms ? We could only do so if 

 we had any proof that Angiosperms were either developed 

 from Gymnosperms, or that both had arisen from the same 

 ancestral Cryptogam, but had become differentiated later on, 

 due to environmental conditions. But evidence goes to show 

 that neither of these two alternatives has taken place ; the 

 embryo-sac of Gymnosperms does not correspond to the em- 

 bryo-sac of Angiosperms, for in the former we are dealing 

 with one macrospore forming a true prothallus (the endo- 

 sperm) developing archegonia ; while if the latter was one 

 macrospore, we would have to consider the division of the 

 primary nucleus as the division of the contents of a macro- 

 spore into a sexual and a vegetative part, according to the 

 view generally held, without being able to explain the con- 

 jugation of the nuclei. If, on the other hand, we regard the 

 embryo-sac as representing two prothalli, we must hold that 

 reduction of one female prothallus has taken place to allow 

 another female prothallus to develop. Such unselfishness 

 does not occur amongst plants, for if anywhere, then in develop- 

 ing macrosporangia a struggle for existence becomes evident. 



That male prothalli are always more reduced than female 

 prothalli amongst Cryptogams and Conifers is well known, 

 but we must be on our guard as to drawing any conclusions 

 with regard to the size of the female prothallus, whenever 

 the male prothallus has become reduced to a single cell ; 

 for in Salvinia, Marsilea, Pilularia, Sclaginella, and others, 

 only one male prothallus-cell is formed, while the female 

 prothalli of these plants attain various degrees of develop- 

 ment. It is quite conceivable that in Angiosperms, where 

 the pollen-grain is shed and where it has to form a long 

 pollen-tube, reduction should not have occurred to the same 

 degree as has taken place in the spores of the embryo-sac. 

 The synergidal cells are " reduced even beyond an oosphere " 

 condition, as they are only capable of passing on the male 

 element to their more vigorous companion, the egg-cell or true 

 oosphere ; but how our accepting Warming's view as to the 

 spore-nature of the contents of the embryo-sac necessitates 

 that the " egg-cell " is reduced beyond an oosphere, I am 

 unable to see. 



I asserted that the eight spores differed in their sex. This 



TRANS. BOT. SOC. VOL. XIX. L 



