ROBERT BROWN 91 



ovule as consisting of a " nucleus " (nucellus) covered by 

 two integuments, save at the apex, where a micropyle 

 was left to facilitate impregnation. The vascular supply 

 in the raphe, the formation of the endosperm and the 

 relation of the embryo to that and other morphological 

 structures, are all described, save for small differences in 

 terminology, exactly as you would be expected to describe 

 them to-day in an examination paper. His investigation 

 of the female cones of the Cycadaceae and Coniferae led 

 him to believe that in some cases the ovules might not 

 be enclosed in carpels and that the pollen might reach the 

 micropyle directly without being first received by the 

 stigma. These considerations induced him to regard 

 these orders as naked - seeded, or gymnospermatous. 

 He also recognised polyembryony in the Gymnosperms, 

 although he did not publish any observations on the 

 subject until long afterwards. He found that the 

 nucellus of the ovule must be distinguished from what 

 he termed the " amnios " or endosperm, and within the 

 amnios he identified three or more clearer regions, each 

 after fertilisation containing a branched thread or threads, 

 at the free ends of which the embryos were developed. 

 He termed these clearer regions " corpuscula," adopting 

 the name from the French botanist Du Petit Thouars, 

 who had also observed them in Cycas. 



You will recollect how, at the end of the eighteenth 

 century, the subsequent history of the pollen grain 

 after it had reached the stigma was left undecided, and 

 how it was very generally believed that the embryo was 

 present in the ovary previous to pollination and merely 

 stimulated to renewed activity in some mysterious way 

 by an oil or other excretion formed on the stigma. Hazy 

 ideas of this kind were quite repugnant to a man of 

 Brown's temperament, who, in all his work, insisted on 

 accurate observation as opposed to vague theorising. 

 An opportunity presented itself to him in 1831 to solve 

 the riddle while examining the flowers of the Orchidaceae, 



