EMBRYOGENESIS IN FLOWERING PLANTS 249 



many resemblances to the Myosurus type, except that in the latter the 

 embryonomic laws apply to the whole of the proembryo, whereas in 

 the former they apply only to the further development of the terminal 

 cell of the two-celled proembryo, Lebegue justifies his (and Soueges') 

 classification of embryo types, as compared with Johansen's classifi- 

 cation, by the statement : 'What matters in an embryo is the embryonic 

 body which contains in its cells the future plant and its vital potenti- 

 ahties. The suspensor characters appear to be relatively less important 

 and should be treated as secondary and subordinate characters in a 

 classification.' The present writer does not entirely agree with this 

 view: the embryo grows as a whole and must be analysed as such. 



From a comparison of the two series or lines, Cruciferae, Reseda- 

 ceae, etc., and Saxifragaceae, Crassulaceae, etc., Lebegue concludes that 

 these are parallel evolutionary series that could have evolved from a 

 common stock — the Ranales. These embryological studies, however, 

 do not yet admit of the construction of a phylogenetic classification. 

 Certain groups, e.g. Cruciferae, Resedaceae and Capparidaceae, 

 possessing embryos of the Myosurus type, are evidently closely related ; 

 but they are very different embryologically from groups considered by 

 taxonomists to be related to them, e.g. Papaveraceae and Fumariaceae. 



ANOMALOUS EMBRYOS 



Embryos, whether of dicotyledons or monocotyledons, with ano- 

 malous segmentation patterns, are important in that they emphasise the 

 fact that the embryo grows as a whole and that this integrated whole- 

 ness is the phenomenon of major importance. The cellular pattern, 

 though it exercises an effect, is essentially subordinate to the overall 

 growth development. Thus we may note that, notwithstanding the 

 numerous embryonomic types that have been specified on the basis of 

 the segmentation pattern, all of them at maturity share very much the 

 same organisation of cotyledons, shoot and radicle. Indeed, unless the 

 whole embryogeny had been worked out, it would be impossible to 

 relate the several organs and tissues to the initial segmentation pattern. 

 The constancy of destination of the cells derived from the four-celled 

 proembryo, as emphasised by Soueges, has been challenged by several 

 investigators, e.g. Borthwick (1931) and Bhaduri (1936). They argue 

 that in related species, or even in the same species, each cell of the 

 proembryo does not invariably give rise to the same part of the mature 

 embryo. 



GENERAL COMMENTARY 



Embryologists have now produced a mass of precise observations 

 on the embryonic development of a large number of species. Their 



