130 BOTANICAL GAZETTE [FEBRUARY 
little has been done in the investigation of the origin of the coty- 
ledons in the typical dicotyledons, especially by the use of series 
of cross-sections which are often indispensable in getting the 
correct orientation of parts. It may be that in many so-called 
typical dicotyledons there is much variation from what has been 
described as the accepted origin of the cotyledons. This can be 
determined only by a thorough and detailed study of a large 
number of forms. 
In Podophyllum the primordium of the cotyledons appears 
first as a rather broad outgrowth from the margin of the trun- 
cated distal end of the embryo, forming an almost complete ring. 
This is made clear by a series of cross-sections such as jig. 4. 
In this figure a and 6 are sections through the broad part of the 
embryo just beneath the primordium of the cotyledons; ¢, through 
the plumule and the base of the ridge; d—/ include the remainder 
of the cotyledonar primordium. From this figure it is apparent 
that the cotyledons arise as a single primordium which consists 
of a circular ridge broken at one side by a notch or indentation. 
As soon as the ridge has attained a little height, a notch is formed 
on the opposite side, and we have now two divisions or lobes 
which will develop into what are considered as two cotyledons. 
The figure shows that one lobe is slightly longer than the other; 
but this is not of importance, because in other preparations the 
two were found frequently to be of equal size. 
A later stage is shown in fig. 7. The bottom of the first notch 
together with the cotyledonar primordium has undergone intef- 
_calary growth, so that a very short tube has been formed. This 
series shows that both the ridge and the lobes have increased in 
height, but the lobes have grown the more rapidly, because their 
height is now about equal to that of the ridge (compare jig. 6), 
and are of equal size. The open ridge is more prominent at this 
time than in younger or older Stages, the notch first formed being 
about twice as deep as the other. 
