1922] BUCHHOLZ—VASCULAR PLANTS 285 
mutation, but it is a powerful mechanism whose censorship may 
determine whether or not any particular intracellular phenomena 
causing mutation may complete the life cycle to be heritable, and 
therefore recognizable as a mutation. 
UNIVERSITY OF ARKANSAS 
FAYETTEVILLE, ARK. 
LITERATURE CITED 
1. Brown, R., in Krnc’s Survey of the western and intertropical coasts of 
Australia. London. 1826 (Appendix B, p. 557); also Am. So. Nat: I. 
8:211. 1826. 
- BrucuMann, H., Uber Selaginella spinulosa. 1897 
. , Uber die Prothallien und die Keimpflanzen mehrerer Europaischer 
Lycopodien. 1898 (pp. rr. pls. 1-8). 
B Lz, J. T., Suspensor and early embryo of Pinus. Bor. Gaz. 
66:185-228. pls. 6-10. figs. 3. 1918. 
, Polyembryony among Abietineae. Bor. GAz. 69:153-167. figs. 
I5. 1920. 
w N 
= 
- 
- ———., Embryo development and polyembryony in lagen to the 
bhyloemiy of conifers. Amer. Jour. Bot. 7:125-145. 
- CAMPBELL, D. H., On the prothallium and embryo of Dasaide oo 
and Gas cinnamomea. Ann. Botany 6:49-04. pls. 3-6. 189 
. ecent investigations upon the embryo sac of angiosperms. 
Amer. Nat. 36:777-786. figs. 5. 1902. 
The sae tig i embryo of Boirychium obliquum. Ann. 
Botany 35:141-158. pl. 
10. CHAMBERLAIN, C. J., Prothallia 2. neta of ape ee Zealand 
species of Lycopodium. Bor. Gaz 4. pls. 2, 3. 
11. Courter, J. M., and bis 3 x 2 Maceeay of POG 
Chicago. 1910 and 1917 
, Morphology me angiosperms. New York. 19093. 
13. CooK, Mt. T., Polyembryony in Ginkgo. Bor. Gaz. 36:142. 1903 
14. CoRRENS, C., Die Konkurrenz der Mannlichen und die weiblichen Keim- 
zellen und das Zahlverhiltnis der beiden Geschlechter. Naturwissen- 
schaften 6:277—280. 1918. 
, Versuche bei Pflanzen das Geschlechtsverhaltnis zu Vershieben. 
Hereditas 2:1-24. 1921. 
16. Dupter, A. W., The gametophytes of Taxus canadensis. Bort. Gaz. 
64:115-136. 1917. 
17. East, E. M., and Park, J. B., Studies on self sterility. II. Pollen 
tube growth. Genetics 3:353-366. 1918. 
18. Farmer, J. B., On the embryogeny of Angiopteris evecta. Ann. Botany 
6: 263-270. 1892. 
~~ 
