144 
JOHN T. BUCHHOLZ 
Summary 
This brief review has summarized, or taken into account, practically 
all of the published work on the embryogeny of conifers in the proembryo 
and early embryo stages. It is shown how the known facts may be har- 
monized under the conception that the Coniferales have been derived from 
forms with cleavage polyembryony, and that this feature tends to be 
more or less eliminated as we pass from the lower to the higher forms. 
The apical cell, cleavage polyembryony, rosette embryos, rosette cells, 
and the direct organization of embryo initials from the free nuclei of the 
proembryo, are regarded as primitive features, while the organization of 
embryo initials after walls form in the proembryo, a proembryo that fills 
the entire egg with cells, the archegonial complex, the embryo cap, and the 
return to simple polyembryony, must be regarded as advanced or specialized 
features. Transitional conditions may also be recognized, and some of the 
vestigial characters, in disappearing by gradual steps, make this interpreta- 
tion of the direction of evolution from cleavage polyembryony back to 
simple polyembryony very certain. Embryogeny must occupy a much 
more important place in the comparative morphology of conifers than has 
generally been conceded. 
University of Arkansas, 
Fayetteville, Ark. 
LITERATURE CITED 
Additional citations on the embryogeny of Abietineae with review may be found in the 
writer's paper on Abietineae (4). 
1. Arnoldi, W. Beitrage etc. V. Weitere Untersuchungen der Embryogenie in der 
Familie der Sequoiaceen. Bull. Soc. Imp, Nat. Moscou, n.s. 14: 449-476. pis. 
7-8. 1900. 
2. Buchholz, J. T. Suspensor and early embryo of Pinus. Bot. Gaz. 66: 185-228. 
pis. 6-10, figs. 3. 1918. 
3. . Studies concerning the evolutionary status of polycotyledony. Amer. Journ. 
Bot. 6: 106-119. figs. 25. 1919. 
4. . Polyembryony among Abietineae. Bot. Gaz. 69: 153-167. figs. 15. 1920. 
5. Burlingame, L. L. The morphology of Araucaria hrasiliensis III. Fertilization, the 
embryo, and the seed. Bot. Gaz. 59: 1-39. pis. 1-3. 191 5. 
6. Chamberlain, C. J. The living cycads. Chicago, 19 19. 
7. Chrysler, M. A. The medullary rays of Cedrus. Bot. Gaz. 59: 387-396. figs. 7. 
1915- 
8. Coker, W. C. Notes on the gametophytes and embryo of Podocarpus. Bot. Gaz. 33: 
89-107. pis. 5-7. 1902. 
9. . On the gametophytes and embryo of Taxodium. Bot. Gaz. 36: 1-27, 1 14-140. 
pis. 1-2, 1903. 
10. . Fertilization and embryogeny of Cephalotaxus Fortunei. Bot. Gaz. 43: i-io. 
pi. I, figs. 5. 1907. 
11. Cook, Mel T. Polyembryony in Ginkgo. Bot. Gaz. 36: 142. 1903. 
12. Coulter, J. M., and Chamberlain, C. J. Morphology of Angiosperms. New York, 
1903. 
13. , . Morphology of Gymnosperms. Chicago, 1910 and 1917. 
14. , and Land, W. J. G. Gametophytes and embryo of Torreya taxifolia, Bot. Gaz. 
39: 161-178. pis. A, 1-3. 1905. 
