ence 
1905] CURRENT LITERATURE 471 
derived from a form not unlike Targionia by adaptation of the gametophyte to 
shady and damp situations, and by changes in the sporogonium induced by the 
alterations in the gametophyte.—J. M. C. 
Drimys, a genus of the Magnoliaceae, and a neighboring genus, Trochoden- 
dron, have long been known to resemble gymnosperms in the structure of their 
wood, which consists entirely of tracheids with bordered pits. Hatter, in his 
Tecent scheme of phylogeny, places Drimys in the Drimytomagnoliaceae, an 
hypothetical group of the Magnoliaceae derived from the Bennettitales or nearly 
telated Cycadales. A paper by STRASBURGER?° gives the results of’a study of 
the ovule, embryo sac, fertilization, and endosperm and early stages in the devel- 
opment of the embryo of Drimys Winteri. In all these particulars the devel- 
opment is that of a typical angiosperm, with not the slightest suggestion of 
gymnosperm characters! 
STRASBURGER takes this occasion to express his views as to the nature of the 
endosperm and embryo-sac structures. The formation of endosperm is still 
regarded as a continuation of an interrupted development of the prothallium, 
the fusion of polar nuclei which precedes it being a secondary phenomenon. In 
the usual development of the embryo sac the two polar nuclei lie in a mass of 
cytoplasm surrounded by a common plasma membrane. Under such conditions 
itis usual for nuclei to fuse. The synergids are not regarded as eggs, but rather 
as cells of the prothallium. The condition found in the ovules of Gnetum is not 
tegarded as a forerunner of the condition found in the embryo sacs of angiosperms. 
Gnetum is rather the last member of a line of development.—CHARLES 
ERLAIN. 
Wiesner has recently written several papers on leaffall,2* one of which, on 
summer leaffall, has been reviewed in the BoTantcaL Gazette.” A second 
Paper deals with Trieblaubjall, or leaffall in connection with the development of 
external factors which so strongly influence leaffall in summergreens are : 
account here. The third paper treats of frost leaffall. If the absciss layer 
_ freezes, the leaf drops at once, but if the rest of the leaf freezes, while the absciss 
layer remains unfrozen, leaffall occurs more slowly. In some cases leaffall is 
due to high turgescence in the cells of the absciss layer. The final =. is a 
Presentation of the biological significance of leaffall, and the author's con a 
are the result of many years of investigation. Leaffall is absent in plants where 
. . 
os 20 STRASBURGER, E., Die Samenanlage von sgh Winteri und die Endosperm- 
ildung bei i -are—271. pls. 7-8 1905- 
g bei Angiospermen. Flora 95:215~231 a eat Die emg 
:316-323- 1904- Ueber Frostlaub- 
fall nebst Bemerkungen iiber die Mechanik der Blattablosung. Jdem 23: 49-60. 
1905. Die biologische Bedeutung des Laubfalles. Idem 23:172-181. 1995. 
*2 Bor. GazETTE 38:153. 1904- 
