EXPERIMENTAL EMBRYOLOGY 



395 



The shape and contents of the cells closely resembled those of the 

 integumentary tapetum and they also showed the diploid number 

 of chromosomes. It is concluded, therefore, that these structures 

 were derived by a proliferation of the cells of the integumentary 

 tapetum, as is the case with many adventive embryos. However, 



A B 



Fig. 210. Artificial production of adventive embryos in Oenothera lamarckiana 

 (s = wound caused by pin-prick; e = ovular epidermis; e.s. = embryo sac; i = inner 

 layer of inner integument; n = nucellus; ne = nucellar embryo). A, diagram of 

 ovule punctured on upper side by fine needle; note two embryos inside embryo sac. 

 B, enlarged view of two embryos. (After Haberlandt, 1921.) 



in view of their undifferentiated nature and the obscurity regard- 

 ing their final fate or potentialities, Van Overbeek et al. wisely 

 refrain from calling them true embryos and designate them as 

 ' 'pseudoembryos . ' ' 



Of considerable interest in this connection are also the recent 

 observations made by Fagerlind (1946) on Hosta. Adventive em- 



