aia ac a a) a Sl ea 
1905] CURRENT LITERATURE 79 
ments, and also sent him much of his artificially produced hybrid material, par- 
ticularly of Hieracium. The letters were written with great care, and as they 
report many hybrids that were not mentioned in MENDEt’s published works, 
they are an important addition to the literature of hybridization. CORRENS 
has carefully annotated the letters and added two appendices, in the first of which 
he discusses the bearing of parthenogenesis upon MENDEL’s results in Hieracium, 
pointing out that these letters can leave not the slightest doubt that true hybrids 
were secured, but inferring from the constancy of the hybrid forms in successive 
generations that there is no reduction division, and that consequently, following 
STRASBURGER, we should speak of apogamy rather than parthenogenesis in Hier- 
acium. In the second appendix CorReEns considers the question whether sexual 
characters are inherited according to MENDEL’s principles, such a possibility 
having been suggested in one of these letters. After examining the various pos- 
sible assumptions as to dominance and the purity or the hybrid character of the 
gametes with respect to sex, he concludes that sex-determinants are fundamentally 
unlike the ordinary character-units and incapable of being satisfactorily explained 
by the laws of dominance and the segregation of parental gametes.—G. H. SHULL. 
LeEwis® has investigated the development of Phytolacca decandra, his main 
purpose being to follow the origin and fate of the endosperm, with special reference 
to its behavior during germination. The development of the microsporangium 
follows the usual course, the tapetal cells perhaps deserving mention in that 
they sometimes contain six nuclei, the average number being four. In the 
megasporangium one and sometimes two archesporial cells appear, and a tapetal 
cell is cut off. The endosperm grows rapidly, ‘‘forming a sac with a great central 
vacuole.” The nuclei lie free in the cytoplasm of the endosperm and always 
divide amitotically. The embryo sac finally becomes the extensive cavity char- 
acteristic of campylotropous ovules. Walls later begin to appear in the micropy- 
lar endosperm, the cells encroach on the central cavity, and finally the endosperm 
is completely cellular except for a mass of cytoplasm at the chalazal end of 
the sac. The embryo in its early stages consists of a well-developed suspensor 
and a many-celled, undifferentiated, spherical embryo. Starch is observed to 
accumulate in the perisperm, notably next to the concavity of the curved embryo, 
which disorganizes the endosperm almost completely. In germination the 
embryo elongates, and the radicle is pushed through the endosperm cap and 
the seed coat. The cotyledons continue to elongate until the stem tip is free, 
and the cells of the thick endosperm cap remain turgid, persisting ‘‘as a thick 
Ting of tissue clasping the bases of the cotyledons and stopping the opening 
made in the seed coat at germination.” —J. M. C. 
PU acres 
aoe Lewis, I. F., Notes on the development of Phytolacca decandra L. Johns Hop- 
Kins Univ. Cire. No. 178. pp. 35-43. pls. 3. 1995. 
