1909] _ CURRENT LITERATURE 313 
fourth, so that the outer nuclei are more widely separated than the rest. These 
more scattered nuclei are sexually functional, while the more crowded ones in the 
inner three-fourths of the sac give rise to the endosperm. Incomplete wall- 
formation occurs, dividing the sac into irregular and multinucleate compartments, 
those of the upper fourth usually containing not more than six nuclei, while those 
of the lower three-fourths contain twelve or more nuclei. ‘The outer multinucleate 
cells develop tubular prolongations (prothallial tubes) into the nucellus, into 
which the nuclei and most of the cytoplasm pass. Occasionally these sexual 
nuclei fuse within the prothallial tube. In the multinucleate cells of the inner 
three-fourths of the sac the nuclei seldom divide, but all fuse, forming uni- 
nucleate cells. This endosperm, consisting of uninucleate cells whose nuclei 
are formed by the fusion of what the author regards as potential gametes, he calls 
a trophophyte, to distinugish it from both gametophyte and sporophyte, and says 
that it “differs fundamentally from the prothallus of the lower gymnosperms,” a 
statement which will have to be amended in a way that will make the proposed 
name seem unnecessary. 
When connection is established between the tip of a pollen tube and of a 
prothallial tube, “the leading female nucleus enters the generative cell within 
which fertilization occurs,” which is certainly a remarkable performance. 
n embryo-formation, the fertilized egg elongates to form a proembryonal 
tube, toward the tip of which the nucleus moves and divides, when a tip cell is 
cut off by an ingrowing wall, just as in Gnetum. The tubular cell of the pro- 
embryo continues to elongate, while the tip cell develops the embryo, which 
consists of about sixty cells when its tip reaches the endosperm. 
The author enters into a somewhat extended discussion of the general bear- 
ings of the facts he has uncovered, a discussion which will be considered in another 
connection.—J. M. C. 
Mechanism of photeolic movements.—LEPESCHKIN, whose investigations of 
turgor mechanisms have been already extensive and important, has added a study 
of the mechanism concerned in the so-called sleep movements of leaves, which he 
be suggested. Long sinceS I proposed for the sleep movements the term photeolic 
movements, avoiding thus the false implications of sleep, nyctitropic, and photo- 
Rastic.) Without referring to the divergent views of various authors on which his 
ae 
‘4 LepEscHKin, W. W., Zur Kenntnis des Mechanismus der photonastischen 
Variationsbewegungen und der Einwirkung des Beleuchtungswechsels auf die Plas- 
mamembran. Beih. Bot. Centralbl. 242308-356- 1909. Preliminary paper: Zur 
Kenntnis des Variationsbewegungen. Ber. Deutsch. Bot. Gesells. 26a:724-735- 1908. 
x HEALD, F. D., Contribution to the comparative histology of pulvini and the 
Tesulting photeolic movements. Bor. GAZETTE 197480. 1894. . 
