620 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
divisions of the nucleus during the formation of the pollen-cells, and in 
the division of the mother-nucleus of the endosperm. 
Embryology and Formation of Endosperm in Taxus.* — Herr L. 
Jaeger has followed out these processes in the yew. The following are 
the more important results. At an early stage the nucellar tissue con- 
tains, in addition to the nuclei, a number of minute sharply -defined 
bodies, which are stained blue by haemalum, closely resembling the 
aleurone grains of the endosperm cells. The original embryo-sac- 
mother-cell was not detected ; the embryo-sac is the result of the en- 
largement of the lowest of a row of cells derived from the original 
mother-cell More than one embryo-sac was never observed. In the 
formation of the endosperm within the embryo-sac the nuclei always lie 
on the wall of the sac. The number of nuclei usually amounts to 256 
when the formation of the cell-walls commences ; this is followed by the 
formation of endosperm (the female prothallium) also in the interior of 
the embryo-sac. The formation of the archegones takes place while the 
endosperm is still rather small; they result from the enlargement of 
cells in the upper part of the endosperm, but subsequently occupy a 
lower position. They contain either one or two nuclei ; the number 
subsequently increasing to four, five, or six, in addition to aleurone 
grains, starch, oil, and a small quantity of albumen. 
The pollen-tubes enter the nucellar tissue when the embryo-sac is 
still very small. The ovum is simply a comparatively large nucleole, 
about double the size of the pollen-nucleus, although the amount of 
active nuclear substance is about the same in both at the period of im- 
pregnation. The impregnated ovum-cell lies in the lowest part of the 
archegone. Cell-formation does not commence until the number of 
nuclei amounts to 16 or 32. 
The formation of the embryo is described in detail. It is common 
for several to be formed in consequence of the entrance of several pollen- 
tubes into the apical portion of the endosperm ; but only one developes. 
At the time when the embryo has become an eight-celled body, the eight 
cells lying in two layers, the four cells of the upper layer elongate into 
embryonal tubes, the number of these tubes subsequently increasing to 
six or more. The true embryo is formed from these embryonal tubes, 
though they do not all take part in its formation. 
The number of cotyledons is usually two, occasionally three. 
(2) Nutrition and Growth (including 1 Germination, and Movements 
of Fluids). 
Localised Stages of Development in Plants and Animals.f — Start- 
ing from the laws that, in the young organism, stages are found, the 
equivalents of which are to be sought in the adults of ancestral types ; 
and that in old age stages are found which are similar to stages found 
in the young; Mr. E. T. Jackson further propounds the following 
laws : — that, “ Throughout the life of the individual, stages may be found 
in localised parts which are similar to stages found in the young, and the 
equivalents of which are to be sought in the adults of ancestral groups ” ; 
* Flora, lxxxvi. (1899) pp. 241-88 (5 pis.). Cf. this Journal, ante, p. 504. . 
f Mem Boston Soc. Nat. Hist., v. (1899) p. 89-153 (10 pis.). 
