GENERALISED SCHEME OF MORPHOGENESIS 



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A. Zygote or spore with sub-microscopic organisation 

 and a specific genetical constitution (comprising 

 nuclear and cytoplasmic genes) which control meta- 

 bolic processes in the cytoplasmic substrate. 



B. Under suitable environmental conditions, gene- 

 controlled enzymes, auxins, etc., become available 

 and active; nutrients are taken up, or mobilised 

 from reserves in the zygote; growth begins. 



C. The polarity of the enlarging embryo is determined 

 by inherent factors and factors in the environment, 

 the initial partition wall being at right angles to the 

 axis. 



D. On further growth, the dispositions of the succeeding 

 partition walls are in general conformity with the 

 principle of cell division by walls of minimal area. 



C^D^. Concomitantly with C and D, a differential utilisa- 

 tion of metabolites at the apical and basal poles is 

 established, the former becoming the locus of active 

 protein metabolism and meristematic activity. 



E. Increase in size brings changes in spatial relation- 

 ships: there is a decrease in the ratio of surface to 

 volume, a separation of parts and the distinction of 

 superficial and inner tissues; the specific diff"usion 

 reaction system in the apical meristem determines 

 the patternised distribution of metabolites and this 

 constitutes the basis for the inception of organs and 

 tissues. 



E^. Concomitantly with C, D and E, biophysical and 

 physical factors become incident and have a large 

 share in determining form and structure; also, 

 growth centres and their physiological fields are 

 established and diffusion gradients set up; and these 

 are important in determining the integrated, regu- 

 lated or harmonious development of the organism. 



F. The distal apex continues as a self-determining mor- 

 phogenetic region, the tissues to which it gives rise 

 becoming the mature, rigid tissues of the axis. 



The Organisation — the regulated inception and 

 development of form and structure — characteristic 

 of the species becomes manifest as development 

 proceeds. 



