328 
M. R. ENSIGN 
seedlings seems to indicate that, if we admit that rejuvenescence has 
occurred at all, it has occurred to the same degree in apogamous and 
gametic plants. And in the light of the more recent work of Child (1915), 
Conklin (1913), and Woodruff (1914), we may conclude that sexuahty is 
not necessary to rejuvenation. 
That the process of ''undifferentiation" and sexuality often occur at 
approximately the same period in the life cycle of the organism is not denied. 
Indeed, the reduction or "undifferentiation " of the organism to a single 
cell is essential before fertilization can occur, but by this reduction rejuvenes- 
cence is already effected independent of any fusion which may or may not 
occur later. Providing the necessary conditions for development surround 
the single-celled embryo, whether it is stimulated to activity by a sperm, or 
a needle prick, or certain physiological conditions, is of little moment so 
far as rejuvenescence is concerned. It is not impossible that the similar 
physiological conditions surrounding the polyembryonic embryos in their 
development may explain the similarities noted in the seedlings. The 
primary function of sexuality it would seem is the production of new char- 
acter combinations in the offspring through the redistribution of distinctive 
ones found in the parents. This view is substantiated by the work of 
Jennings (1912) and Woodruff (1914), who show that protozoa are poten- 
tially immortal, and that sexuality serves the sole purpose of producing 
favorable variations. 
Summary 
1. Germination tests showed that 43.18 percent of the seeds of Citrus 
grandis produce polyembryonic shoots. 
2. A new method for clearing and staining leaves is described. 
3. The size of vein-islets is not correlated with the shape and location 
of the islets in leaves of C. grandis. 
4. The size of the vein-islets is directly correlated with the maturity 
of the ^eaf. From the most immature to the fully matured leaves there is 
a gradual increase in the size of vein-islets. 
5. In mature leaves the size of the vein-islets is quite constant, inde- 
pendent of the size of the leaf. 
6. The size of vein-islets in mature leaves from chlorotic, stunted plants 
is the same as in mature leaves from healthy plants. 
7. The size of vein-islets revealed no difference between polyembryonic 
seedlings arising from a single seed. No doubt the individuals composing 
some of these polyembryonic pairs were of gametic and apogamous origin 
respectively. 
8. The nucleo-cytoplasmic ratio, as determined in the meristem of the 
root tips from polyembryonic plants, is essentially the same in gametic 
and apogamous plants. 
9. Difference in size of polyembryonic seedlings seems to be a matter 
