STUDIES CONCERNING THE EVOLUTIONARY STATUS OF 
POLYCOTYLEDONY 
John T. Buchholz 
The question which condition is more primitive, polycotyledony or 
dicotyledony, has been very widely discussed and is a very old subject in 
botanical literature. It is generally believed that one of these has been 
derived from the other, and for more than seventy years botanical opinion 
has been divided on the question. On the basis of anatomy, Duchartre, 
in 1848, supported the thesis which had been previously announced, that 
polycotyledony has been derived from dicotyledony, but this view was not 
accepted by Sachs in his text-book (1882). Masters in 1 891 supported the 
views of Sachs, and Dangeard supported the older view of Duchartre. More 
recently. Hill and DeFraihe (6), after the study of the vascular anatomy of 
many conifer seedlings, also reached the conclusion that polycotyledony 
has been derived from dicotyledony by a splitting of the cotyledons. 
Hill and DeFraine find that in most instances there is a single vascular 
strand in the cotyledon. They classify as whole-cotyledons those in which 
this strand undergoes bifurcation accompanied by a rotation of the xylem 
to bring the protoxylem in the exarch position as it forms a single root pole ; 
as half-cotyledons those in which the strands from two cotyledons combine 
during transition to form one root pole; and as subsidiary-cotyledons those 
in which the strand fuses with another above the transition region. The 
existence of intermediate stages leads these authors to infer that "a sub- 
sidiary seed-leaf may, in the course of events, be promoted, as it were, to 
the rank of a half-cotyledon; while a half-seed-leaf may be raised to the 
dignity of a whole-cotyledon." In addition to this, they find that occa- 
sionally leaves from the plumule may become displaced and added to the 
cotyledonary node. 
The argument of Hill and DeFraine rests further upon the existence of 
cotyledons with double strands, partially divided cotyledons, and numerous 
similar abnormalities. The theory is more plausible when applied to the 
Taxineae, Podocarpineae, and other forms with few cotyledons, but be- 
comes very difficult to explain for the more extremely polycotyledonous 
Abietineae. While these authors make use of the external anatomy in their 
hypothesis, they give us no explanation for the origin of the cotyledonary 
tubes which they found in many instances among twenty species — nearly 
one third of the number investigated. 
On the other hand, assuming that when two cotyledons fuse they form 
double cotyledons, which later lose their double nature, and that the cot- 
106 
■i 
