232 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The process appears to be similar in Juniperus communis ; but here 
one pollen-tube serves for the impregnation of several oospheres. 
Constriction and Partial Obliteration of the Embryo-sac.* — Herr 
F. Hegelmaier describes the peculiar processes which take place in the 
development of the embryo-sac of various species of Linum (^catharticum, 
fiavum, austriacum, grandiflorum, angustifolium, and usitatissimum). In 
the two last-named species the embryo-sac, in the course of its develop- 
ment, broadens chiefly at its upper (oosphere) end, the lower (antipodal) 
end remaining comparatively narrow, and these two portions become 
gradually separated from one another by a constriction. The upper 
portion contains the embryo, and in it alone formation of endosperm 
takes place. The narrower portion becomes eventually entirely sepa- 
rated, still inclosing the antipodals, and, in its upper part, a number 
of nuclei, the origin of which is doubtful. It at length becomes com- 
pressed by the growing fertile portion of the sac, and almost unrecog- 
nizable. In L. grandiflorum the process is similar, except in the different 
shape of the sterile portion of the sac. 
In L. catharticum the process is somewhat different. No constriction 
of the embryo-sac takes place ; but its lower portion becomes obliterated, 
and converted into a solid curved cord, the remains of the antipodals 
being still visible in the fertile portion. L. fiavum presents similar 
phenomena. 
A third mode of obliteration occurs in L. austriacum. A constriction 
is formed in a mode similar to that in the first-named species ; but the 
separation of the two parts of the embryo-sac is only temporary, a 
portion of the contents of the upper part being subsequently again 
forced into the lower part. 
The nuclei found in the upper part of the sterile portion may either 
have arisen independently, or they may be products of division of the 
antipodals or of the original nucleus of the endosperm. 
Cleistogamy in Polygonum.f — Mr. T. H. Kearney confirms Mr. 
Meehan’s observation of the existence of eleistogamous flowers in Poly- 
gonum acre , on branches either underground or only just above the 
surface of the soil. 
1(2) Nutrition and Growth (including Germination, and Movements 
of Fluids). 
Assimilation by the Mistletoe.J — According to Prof. G. Bonnier, the 
relationship between the mistletoe and the tree (apple-tree) on which it 
grows, is not one of simple parasitism, but rather one of symbiosis. 
He found that in the summer, at a temperature varying between 15° and 
35° C., the leaves of the mistletoe disengage per weight about 1/6, or per 
surface about 1/3, as much as the leaves of the apple; and the former 
must therefore depend, for the larger part of its nutriment, on its 
parasitism on the latter. In the winter, however, the conditions are 
reversed ; and, by a series of experiments on the dry weight, Prof. 
* Ber. Deutsch. Bot. Gesell., ix. (1891) pp. 257-66 (1 pi.). 
t Bot. Gazette, xvi. (1891) p. 314 (1 fig.). Cf. this Journal, 1S89, p. 781. 
% Bull. Soc. Bot. France, xxxvi. 1891, Actes du Congres de But., 1889, 
pp. cclxxiii-iv. 
