768 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
papillae ; after reaching the ovary they advance along a furrow, which 
is overspanned by threads of mucilage. The micropyle does not open 
of itself, but its cells are pressed apart by the pollen-tubes. The 
embryo-sac is, in this plant, developed directly from a hypodermal 
cell. A few cases of polyembryony were observed, in which the second 
embryo was undoubtedly the result of the impregnation of one of the 
synergidae. The author is unable to confirm Westermaier’s view * that 
the antipodals assist in the nutrition of the embryo ; in Lilium Martagon 
they are undoubtedly without any such function. 
Fertilization of Iris sibirica-t — Prof. A. Dodel has followed out 
the process of the impregnation of the oosphere in this plant. As 
long as the pollen-tubes are penetrating the stigma and style they are 
extremely slender, but increase rapidly in thickness when they have 
entered the ovary. A very large number of pollen-tubes enter the 
ovary, and it is not uncommon for more than one to enter a micro- 
pyle. In that case one or both of the synergidae may be impregnated 
and develope into embryos. The following differences are presented 
between the oosphere and the synergidae ; the nucleus of the former 
contains a distinct spherical nucleole ; those of the latter do not contain 
distinct nucleoles at the time of impregnation. The nucleus of the 
oosphere lies in its upper part, those of the synergidae in their basal 
portion. A similar difference is exhibited in the distribution of the greater 
part of the cytoplasm; that of the oosphere is full of vacuoles, while that 
of the synergidae contains scarcely any. These facts have led the author to 
the belief that the synergidae must be regarded as partially aborted 
oospheres. It sometimes happens also that two of the sperm-nuclei 
(pollen-nuclei) enter the oosphere, and both coalesce with its nucleus. 
Contrivances for Pollination. f — Herr E. Loew has examined the 
structure of the flower, especially in relation to the facilities for insect- 
pollination, in a number of species belonging to the following natural 
orders : — Berberideae, Papaveraceae, Bibesiaceae, Eosaceae, Primulaceae, 
Hydrophyllaceae, Scrophulariaceae, Solanaceae, Borraginaceae, Labiatse, 
Caprifoliaceae, Liliaceae, Amaryllidaceae, Iridaceae. With regard to the 
fifth barren stamen or staminode in Pentstemon , the author thinks that 
it may serve a variety of purposes ; — the two rows of hairs with which 
it is frequently provided serving to detain the pollen which falls upon 
it, and also to protect the nectaries against the incursion of creeping 
insects. In the genus Narcissus there are, from this point of view, 
five different types of flowers, according as its structure is adapted for 
pollination by humble-bees or by Lepidoptera, or by both classes of 
insects. 
Mr. G. F. Scott Elliot § describes the arrangements of structure in 
nearly 200 S. African and Madagascan Flowering Plants, belonging to 
a great variety of natural orders, which favour cross-pollination by the 
agency of insects, giving also a list of the visiting insects. 
* Vide supra , p. 766. 
f ‘Beitr. z. Kenntniss d. Befruchtungs-Erscheinungen bei Iris sibirica ,’ Zurich, 
1891, 15 pp. and 3 pis. 
X Jahrb. f. Wiss. Bot. (Pringsbeim), xxii. (1891) pp. 445-90; xxiii. (1891) 
pp. 207-54 (4 pis.). 
§ Ann. of Bot., v. (1891) pp. 335-405 (3 pis.). 
