ZOOLOGY AND BOTANY, MICROSCOPY, ETC. I :'•;"> 



When the pollen-tube has reached the embryo-sac, three nuclei — 

 probably the pollen-tube nucleus, the stalk nucleus, and the " body-cell 

 nucleus " — are seen in a group, and all of them pass into the archegone, 

 but the tube and stalk nuclei are at that time undergoing disintegration ; 

 both male nuclei may enter the same archegone. The male and female 

 nuclei come into contact near the upper end of the archegone, and fuse 

 •■completely near the base of the oosphere. The first division of the 

 fertilised oosphere does not seem to be constant in direction. In the 

 next stage the pro-embryo consists of three tiers of four cells each. In 

 the upper tier no cell-walls are found, the nuclei lying free in the cavity 

 of the archegone. The pro-embryo is in this stage very like that of 

 ■Juniperus ; by the elongation of the second tier from the top the embryo 

 is forced out into the endosperm. 



Visits of Birds to Flowers. — E. Werth * discusses the question 

 whether the Nectarinieae (honey-birds) of tropical Africa visit flowers 

 for the sake of the honey, or of the insects which feed on the honey, 

 and concludes, from the structure both of the birds and of the flowers, 

 that the former is generally the case, although the capture of insects 

 may also sometimes be the object ; but the sucking organ is not so much 

 the long tongue, as has been stated, but the beak. 



Prof. F. Dahl f has investigated the same problem in the Bismarck 

 Archipelago. He finds there 3 species of Papageieae, 2 of Meliphagidese, 

 and 2 of Nectarinieae, which visit flowers. From an examination of the 

 contents of the stomach, he determined conclusively that the Papageieae 

 (sp. of Charmosyna) are pollen-eaters, while the Meliphagidese and Nec- 

 tarinieas are entomophagous. No evidence was found that the ento- 

 mophagous birds feed also on honey, and the flowers which they were 

 observed to visit had no nectaries. 



Werth, | in reply, while admitting that an examination of the con- 

 sents of the stomach must be conclusive as to the nature of the food, 

 still maintains that the Nectarinieae feed on honey as well as insects ; 

 otherwise it would be impossible to account for their sucking apparatus. 



Protection against the Germination of Foreign Pollen.§ — W. Burck 

 has observed that different substances have very different effects on the 

 germination of pollen-grains belonging to different species. Thus with 

 Mussendsea [Musssenda ?], even a very small quantity of levulose greatly 

 promotes the emission of pollen-tubes, while saccharose, dextrose, 

 mannite, dextrin, and asparagin have no such influence. With Pavetta, 

 on the contrary, a very small quantity of levulose caused the pollen- 

 grains to burst. Pollen-grains of Canna and Justicia burst in water, 

 but not in a 20 p.c. solution of cane-sugar when a mere trace of levulose 

 was added. He suggests that on the stigma there may be produced, not 

 only substances which promote the production of the pollen-tubes of the 

 particular species, but others also which act injuriously on the pollen of 

 foreign species. 



* S.B. Ges. Naturf. Freunde Berlin, 1900, pp. 73-7 ; and Verhandl. Bot. Ver. 

 Prov. Brandenburg, xlii. (1901) pp. 257-60. See Bot. Centralbl., lxxxvi. (1901) 

 .p. 297. t Tom. cit., pp. 10U-13 (3 figs.). J Tom. cit., pp. 113-7. 



§ S.B. kou. Akad. Wetensch. Amsterdam, Sept. 20, 1900 (English). See Bot. 

 Ztg., lix. (1901) 2" Abt., p. 134. 



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