cook: seedling morphology 425 



This is in line with the suggestion already made in relation 

 to the epiblast. If we consider that two reduced leaves are 

 united in the coleoptile, a similar reduction of leaves immediately 

 above the cotyledon would not seem improbable. The epi- 

 blasts would be in the nature of hypophylls like those that occur 

 on seedlings of the avocada, Persea americana, for several inches 

 above the cotyledons. Epiblasts may be considered as rudi- 

 mentary leaves without supposing that they have been in the 

 past equal partners of the cotyledons, and without adopting the 

 theory that the monocotyledons plants have been derived 

 directly from dicotyledons. Too much stress appears to have 

 been laid upon the number of the cotyledons, in view of the 

 fact that variations are of rather frequent occurrence, and that 

 the two series of plant families approximate rather closely when 

 such groups as the Araceae, Artocarpaceae, and Piperaceae are 

 considered. 



As the metamerous organization of the plant body is espe- 

 cially noticeable in these more primitive members of the two 

 series, there is the greater reason to take this feature into account 

 in attempting to reach a morphological understanding of special 

 structures and functions. The principle of metamerism yields 

 a conception of the plant body as made up of equivalent units, 

 instead of as an axis with leaves and other appendages attached. 



