io8 
JOHN T. BUCHHOLZ 
species, but is found among representatives of different genera taken more 
or less at random and is in harmony with all the known facts, it establishes 
a safe morphological basis for conclusions. 
The cotyledons develop in the other conifers in practically the same way 
as the writer has described for Pinus (2). As pointed out there, the stem 
tip primordium appears before the primordia of the cotyledons. It con- 
sists of a vsmall protuberance at the apex of the dome which crowns the 
cylindrical cell mass of the undifferentiated embryo. Meanwhile, the whole 
embryo mass enlarges, and soon a circle of cotyledon primordia appear 
very nearly simultaneously, surrounding the stem tip. These primordia 
are little protuberances like the stem tip primordium and they soon elongate 
to form the cotyledons. They are separate and distinct from each other 
, Figs. 1-3. Embryos of Pinus Banksiana which are occasionally found, showing coty- 
. ledonary fusion in the primordial stage. X 32. 
when they first appear, and their number is not constant but varies, much 
as does the number of cotyledons that are found in the matured embryo. 
The primordia are formed long before there are any vascular strands. 
The latter are formed only some time after the cotyledons have begun to 
elongate. Therefore, evidence based on the origin of the primordia and of 
the cotyledons from these primordia has much greater morphological value 
than the study of the later appearing vascular structures, and has in addi- 
tion the advantage of being capable of showing a definite recapitulation of 
the more primitive condition. 
The writer has published evidence of cotyledonary fusions in the pri- 
mordial stage of Pinus Banksiana (2). This species has a small number of 
cotyledons, ranging between three and six, the usual number being four. 
Here the number of primordia is sometimes greater than the number of 
cotyledons, and a number of instances were found which showed various 
