54 



Plant Tissue Cult are 



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Pig. 20. Young embryo of Portulaca oleracea with remnants of 

 the embryo sac still adhering. If embryos of this and still younger 

 stages can be grown, much may be learned of the factors involved 

 in early embryo development. ( Prom White, P. K. L932. Arch, 

 exp. Zellf. 1 1 : 610, fig. s, 89. | 



