336 EMBRYOGENESIS IN PLANTS 



The descriptive and pictorial aspect of plant embryology, though by 

 no means complete, is well advanced. On the other hand, with some 

 notable exceptions, little has been achieved in the field of experimental 

 and chemical embryology — certainly nothing that is comparable with 

 the achievements of zoologists. Botanical workers in these fields 

 have been few, possibly because of the technical difficulties in handling 

 the small and usually rather inaccessible embryos. It may be that these 

 difficulties have been over-rated. A determined effort to make new 

 discoveries in experimental embryology is just as likely to succeed as 

 experimental work of apices which, not so long ago, was viewed in 

 much the same way. That pure culture technique can be adapted to 

 embryo culture has been shown by various investigators, while surgical 

 techniques have been successfully attempted, though only to a limited 

 extent. Whitaker and his colleagues have shown what can be achieved 

 in the experimental manipulation of Fucus eggs, D'Arcy Thompson 

 and others have been impressed by the probable importance of physical 

 factors in morphogenetic processes, including those in embryos. It is 

 very desirable that the hypotheses which have been proposed should be 

 tested experimentally. In contemporary studies of physiological 

 genetics, one of the aims is to discover how and when particular genes 

 act to produce their specific growth and morphogenetic effects. The 

 constancy and specificity of the embryonic developmental pattern in 

 flowering plants, and the occurrence of characteristic anomalous 

 developments in certain hybrids, make it probable that embryological 

 investigations of related plants of known genetic constitution may 

 yield information of particular interest. The activation of the ovum 

 at fertilisation, and the nutrition, growth and development of the 

 embryo, undoubtedly afford a wide field for study. 



The foregoing points give some indication of the ways in which 

 botanical science can be advanced by the study of embryos. But it may 

 well be that the really important problems will only be uncovered or 

 envisaged when substantial progress has been made in the experimental 

 work. Lastly, since in embryos we are dealing with cells and tissues, 

 either in the primary embryonic condition, or in the process of becoming 

 differentiated, comprehensive studies of the relevant protein chemistry 

 must be given first place in all investigations that claim to be of a 

 fundamental character. 



