18 ADDRESS TO THE BRITISH ASSOCIATION, 1881. 



morphology, histology, and physiology scarcely existed 

 before 1830. In the two former branches the discoveries 

 of von Mohl are pre-eminent. He first observed 

 cell-division in 1835, and detected the presence of starch 

 in chlorophyll-corpuscles in 1837, while he first de- 

 scribed protoplasm, now so familiar to us, at least by 

 name, in 1846. In the same year Amici discovered the 

 existence of the embryonic vesicle in the embryo sac, 

 which develops into the embryo when fertilised by the 

 entrance of the pollen-tube into the micropyle. The 

 existence of sexual reproduction in the lower plants was 

 doubtful, or at least doubted by some eminent authorities, 

 as recently as 1853, when the actual process of fertilisa- 

 tion in the common bladderwrack of our shores was 

 observed by Thuret, while the reproduction of the larger 

 fungi was first worked out by De Bary in 1863. 



As regards lichens, Schwendener proposed, in 1869, 

 the startling theory, now however accepted by some of 

 the highest authorities, that lichens are not autonomous 

 organisms, but commensal associations of a fungus 

 parasitic on an alga. With reference to the higher 

 Cryptogams, it is hardly too much to say that the whole 

 of our exact knowledge of their life-history has been 

 obtained during the last half-century. Thus in the 

 case of ferns the male organs, or antheridia, were first 

 discovered by Nageli in 1844, and the archegonia, or 

 female organs, by Suminski in 1848. The early stages 

 in the development of mosses were worked out by 

 Valentine in 1833. Lastly, the principle of Alternation 

 of Generations in plants was discovered by Hofmeister. 

 This eminent naturalist also, in 1851-4, pointed out 

 the homologies of the reproductive processes in mosses, 

 vascular cryptogams, gymnosperms, and angiosperms. 



