556 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
derived ; no coalescence takes place with tlie polar nucleus ; this latter 
divides into two or four, corresponding to the antipodals. Finally, 
the whole egg-apparatus — oosphere and synergids — disappears, except 
the polar nucleus, which undergoes division, dividing the embryo-sac 
into a small upper and a large basal cell, of which the former only 
develops, dividing into a small number of endosperm-cells. One of 
these becomes the pseudo-embryo. The endosperm-cells form a large 
amount of oil, and become frothy. The number of cells of which the 
embryo is composed is not more than from five to ten while it is still 
enclosed in the mother-plant. Pollen-tubes were never seen to enter 
the female organ, and the phenomenon is therefore one of pure apogamy, 
resembling that of Pteris cretica. 
Embryogeny of Euphorbia.* — According to observations made by 
Florence M. Lyon on Euphorbia corollata, each single so-called “ flower ” 
is an inflorescence of the same type as the general inflorescence. This 
inflorescence (cyathium) tends to become further reduced by the abortion 
of the terminal (female) flower. The development of the ovule is marked 
by an elaborate outgrowth of the nucellus in the form of a long neck, 
whose direction of growth is guided by placental hairs which exert an 
attractive influence, causing it to bend toward them, thus making a com- 
plete connection between the stigmatic cells and the embryo-sac for the 
passage of the pollen-tube. Ovules appear before there is any trace of 
carpel, being clearly of cauline origin. There is nothing unusual in 
the development of the embryo-sac. The synergids are remarkably long, 
and the antipodals very ephemeral. As a rule a single cell is the an- 
cestor of all the spore-mother-cells in each pollen-sac. The tapete may 
be clearly differentiated, at least one division preceding the pollen- 
mother-cells ; it is developed from the wall. The synapsis stage was 
observed with great regularity. There are indications that the genera- 
tive cell may not divide. 
Embryogeny of the Pontederiacese.f — Mr. W. E. Smith has studied 
the biology of this order, chiefly in Poniederia cordata and Eichhornia 
crassipes, but finds no special ordinal characteristics. The two genera 
agree in the ephemeral nature of the antipodals and in the structure of 
the endosperm. Such irregularities as occur in Eicliliornia appear to be 
correlated with its enormous power of vegetative multiplication. 
How Flowers attract Insects.— Dr. P. KnuthJ subjects Plateau’s 
conclusions on this subject to a critical examination, and arrives at a 
result that they are based on an erroneous interpretation of the facts. 
While admitting that insects may at first be attracted to flowers from 
a distance by their scent, Dr. Knuth still regards colour as the chief 
source of attraction at smaller distances ; the markings on the corolla 
itself being in many cases the final guide-post to direct the insects to 
the ovary. 
Sir J ohn Lubbock § has repeated some of Plateau’s experiments, and 
has arrived at the same result : — that his conclusion that insects are 
attracted mainly by the sense of smell is not substantiated. 
* Bot. Gazette, xxv. (1898) pp. 418-26 (3 pis.). 
f Tom. cit., pp. 324-37 (2 pis.). 
X Bot. Centralbl., lxxiv. (1898) pp. 39-46. Cf. this Journal, ante, p. 191. 
§ Journ. Linn. Soc. (Bot.), xxxiii. (1898) pp. 270-8. 
