210 BOTANICAL GAZETTE [SEPTEMBER 
cap. This curved cell arrangement may be recognized in the 
whole embryos mounted in Venetian turpentine or balsam, but 
sections show the details of this cell organization much better. 
The stem tip may be recognized as a slight protuberance in 
the position formerly occupied by the apical cell, but long after 
this cell has disappeared. It may first be seen in embryos about 
175 ux 400 mw; and in living embryos dissected out under water a 
transparent area develops in the tissues near it, which is shown by 
the shaded area of B, text fig. 3. The embryo enlarges, and by the 
time it has reached the size of D the circle of cotyledonary primordia 
is recognizable. The number of these primordia, like the number 
of cotyledons, is not constant, and ranges from 3 to 7. Although 
the cotyledonary primordia are usually equally developed when they 
first appear, sometimes they are larger or appear sooner on one 
side than on the other. Figs. J and K show cases where 2 
primordia formed only 1 cotyledon. Figs. H and J show the 
same thing in earlier stages, and since stages older than K do not 
reveal a double tip on the broad cotyledons it is doubtless rapidly 
outgrown. Many broad cotyledons may have a similar origin, but 
some of them seem to arise directly from 1 broad primordium. 
Although embryos like H, J, J, and K are not as common as £ 
and F, those that do not show fusing primordia, there is no doubt 
a distinct tendency in P. Banksiana to reduce the number of cotyle- 
dons. The mature embryo frequently has only 3 cotyledons, and 
4 or 5 are the usual numbers. In P. Laricio fusing primordia 
were not found, but here there are usually 10 or more cotyledons, 
and there seems to be no tendency to reduce their number. 
The embryos of these 2 species show a tendency to grow 
slightly zygomorphically. In some cases this seems to date from 
the first appearance of the primordia. It is usually not very 
pronounced, but an embryo of P. Laricio, extremely abnormal in 
this respect, is shown in text fig. 3L. Here the suppression of the 
cotyledons on one side is nearly complete, a condition which, 
in the presence of a cotyledonary tube, would result in an embryo 
similar to the monocotyledonous embryo, as described in recent 
work (11). Although 2 primordia sometimes combine to form a 
single cotyledon, none of these pine embryos have a cotyledonary 
tube at any stage of their development. 
