Proceedings 51 
for considering that the Primitive Flowering Plant—if it 
could be reconstructed by botanists—would be ranked by 
them as an undoubted Dicotyledon. 
Of the five or six characters which separate Monocoty- 
ledons from Dicotyledons, two are very constant indeed: 
the single cotyledon, and the absence of a true cambium 
or thickening-ring in the stem. 
No known Monocotyledon possesses either more than 
one cotyledon, or a true cambium in the mature stem, 
The converse is not quite true. A few Dicotyledonous 
species, scattered among several families systematically re- 
mote from one another, have one cotyledon only, and 
others have lost the cambium ring more or less completely. 
If the seedling of the Primitive Flowering Plant had two 
cotyledons, and its mature stem possessed a true cambium, 
it would certainly be now placed among Dicotyledons, 
There is some evidence to show that it did possess both 
features. 
Recent work in two departments of Botany gives reason 
to believe that the mature stem of the Primitive Flower- 
ing Plant resembled that of a Dicotyledon in possessing a 
cambium. ‘he cumulative weight of this evidence is very 
great, and in the absence of any to the contrary we are 
justified in assuming that the Primitive Flowering Plant 
was provided with a cambium. 
My own work has been chiefly concerned with the second 
question. Had the Primitive Flowering Plant one cotyledon 
or two? The majority of botanists have assumed that it had 
one: a character retained by Monocotyledons. The two coty- 
ledons of Dicotyledons would then be developed by fission 
of the original structure. Those botanists who maintain 
that the Primitive Flowering Plant had two cotyledons 
have, with one exception, assumed that the suppression of 
one gave rise to a monocotylous race, now represented by 
existing Monocotyledons. 
A third view was suggested nearly a century ago by the 
Swedish botanist, Agardh, that the monocotylous form was 
derived from the dicotylous by complete union of the two 
cotyledons. 
