60 postelsia 



hesitatingly regarded the cotyledons as 

 metamorphosed leaves. In fact the 

 envelopes of the flower and the coty- 

 ledons approach so nearly to the char- 

 acter of leaves that every unprejudiced 

 eye must instinctively perceive the re- 

 semblance." This explanation no 

 doubt first grew out of observation 

 upon dicotyledonous seedlings having 

 epigean cotyledons which took on the 

 character of leaves. Comparative study 

 of embryos showed that hypogean cot- 

 yledons were homologous structures, 

 which failed to assume the photosyn- 

 thetic function. The investigations of 

 Gsertner, Poiteau and Mirbel, recorded 

 now for almost a hundred years, es- 

 tablished the fact that the cotyledon of 

 the Monocots was an homologue of that 

 of the Dicots. Poiteau originated and 

 Mirbel supported the doctrine, which re- 

 ceives credence to-day, that the epiblast 



