EVOLUTIONARY STATUS OF POLYCOTYLEDONY 
is clear that if wholesale fusions should occur here it would probably result 
in dicotyledony or in a two-lipped cotyledonary tube. This tendency for 
the cotyledons to develop in two groups may be found in Pinus Laricio, 
P. Banksiana, P. edule, P. Sabiniana, and doubtless in many other species. 
It is not usually found in P. Strohus. 
In Abies balsamea, Juniperus commune, and Thuja occidentalism no evi- 
dences of cotyledonary fusions were found. The cotyledonary number is 
nearly fixed in these species, being usually four and occasionally five in 
Abies balsamea, and usually two, sometimes three, in Thuja and Juniperus. 
Not more than several dozen embryos of each of these species were examined 
in the cotyledon-forming stage, and these all with negative results. 
Abies balsamea has a well developed sinus at the tip of each cotyledon, 
which makes the cotyledon appear strongly retuse. This character is de- 
veloped after the cotyledons have begun to elongate, and is not due to 
fusing primordia as one might suspect in the light of the foregoing studies, 
after examining the cotyledons in any but the earliest stages of their de- 
velopment. 
In his work on Pinus, the writer reported that the cotyledon primordia 
are usually simultaneous in their origin, but exceptions to this were found in 
which the primordia on one side appeared slightly before those on the 
opposite side. This tendency has been observed in Pinus, Larix (see fig. 
19), Picea (see figs. 20-22), and occasionally in Cedrus, but the difference 
between the first and last primordia that appear is never very great. The 
primordia appear so nearly at the same time that on most of the embryos 
this feature is entirely overlooked. Figure 23 shows diagrammatically this 
slight difference in the size of the primordia on the same embryo in an ex- 
treme case, and this is quite frequently found in Picea mariana. It sug- 
gests that the cotyledons are essentially spiral in their origin, that they have 
become cyclic from a previous spiral condition. 
Sometimes a zygomorphic tendency becomes evident some time after 
the primordia have appeared and the cotyledons have begun to elongate. 
The most extreme case of this kind was reported in a half-grown embryo of 
Pinus Laricio (2), and Picea showed several less marked examples. This 
zygomorphy which comes on some time after the primordia have appeared 
is not to be confused with the slight difference in the appearance of the pri- 
mordia themselves, mentioned above. 
The tendency toward spiral development exhibited by these cotyledon 
primordia suggested the idea that this may have been the more primitive 
condition, and made it seem desirable to know more definitely the condition 
of the first leaves of the plumule just above the cotyledons. An examina- 
tion of the seedlings of several Abietineae shows that though the cotyledons 
are cyclic, their first simple leaves are arranged spirally, the condition which 
is well known for the older branches. The following seedlings were in- 
spected: Abies concolor, Pinus Strobus, Pinus Laricio, Pinus Banksiana, 
