208 BOTANICAL GAZETTE [SEPTEMBER 
13, 14, and 15, and no cases of “twin embryos”’ formed by such a 
vertical splitting could be found. The embryos never even show 
tendencies to round off at these nearly vertical cleavages, or upon 
the formation of any wall other than the one which separates the 
4 primary embryos. Such ‘“‘twins’’ would be easily recognized 
in dissected preparations, since they would be found attached by 
their secondary suspensors to a common suspensor, leading back toa 
single primary suspensor cell. 
When the 4 primary embryos are sectioned in stages before they 
are completely separated, it is possible, in rare cases, that 2 
embryos may be so cut as to appear to be at the tip of a single 
suspensor or embryonal tube. This might look as if the 2 
embryos had arisen on the end of the same suspensor by the splitting 
of a single one, especially if some of the adjoining sections are lost. 
The writer had the opportunity of examining the original slide 
from which the drawing of a ‘‘twin embryo” had been published (8). 
Upon critical examination it proved to show traces of the wall of a 
second suspensor cell from which the stain had been washed out, 
and is more correctly shown in fig. 36. One of the adjoining 
sections, which happened to be a very thick one, is missing from 
the slide. It was possibly lost off during the staining, as the 
accidentally thick sections of a series often are, but the recognition 
of this second suspensor cell gives each of the 2 embryos in this 
figure its own suspensor and indicates that these 2 embryos were 
2 of the primary group of 4, sectioned in a rather unusual position. 
The possibility that one of the 4 primary embryos could split to form 
2 has been claimed by several investigators, but no other figures 
showing twin embryos of pines could be found in the literature 
on this subject. 
Another type of twins is that found when 2 of the members of 
the embryo complex develop to fair size to form the mature seed 
embryos. Although polyembryony is such an extensive phe- 
nomenon in Pinus, the writer has never been able to find a mature 
seed with 2 fully and equally developed embryos; one was 
always considerably larger than the other, and these were not 
very common. When these 2 embryos are members of the 
same embryo system, the twin formation is due to a cleavage 
phenomenon, and is similar to that of duplicate twins in animals. 
