864 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENEBAL, including Embryology and Histology 

 of the PJianerogamia. 



Fertilization of the Borraginaceae.* — The change of colour in 

 various borragiuaceous flowers would seem to bear relation to their 

 fertilization. Hermann Mliller remarks that he has observed that 

 insects visit exclusively those which are red or just beginning to 

 change to blue. All the blue flowers which he examined in a locality 

 about 2 yards broad and 20 long, where many hundred flowers of 

 Puhnonaria were in all stages of development, proved to be empty 

 of honey, and all which he observed with the aid of a lens had the 

 stigma already supplied with pollen ; so that it would appear that, 

 as in Lantana and Ribes aiireum, the change of tint serves as a guide 

 to insects visiting the flower. 



Pollination of Cypella.t — Two Brazilian species of this genus of 

 Iridese have been studied from time to time by Fritz Miiller, who 

 finds a number of interesting peculiarities in their flowering. The 

 flowers are produced in abundance only on certain days, which recur 

 more or less regularly, and apparently independently of climatic con- 

 ditions. Nectar is secreted in tlie pockets on the three i^etals, which 

 are flexible, so that when a Xylocopa or Bomhus, to which the flowers 

 seem well adapted, alights on one in quest of nectar, it bends over 

 with the weight of the bee, whose back is brought in contact with a 

 stigma and the underlying anther. Commonly the bee goes to another 

 flower without trying the other petals of the one on which it has first 

 settled, so that crossing is efiected by it. One of the species studied 

 proves to have self-imi^otent pollen ; the other is fertile with its own 

 pollen. The stingless bees (Trigona), though not necessarily ex- 

 cluded by structural peculiarities from the nectar, do not obtain it 

 readily ; yet their visits for the protectively coloured (pale bluish) 

 pollen are sufficiently numerous to prevent the larger bees from 

 visiting the flowers in numbers. 



Pollination of Rutacese.| — J. Urban has studied the adaptations 

 for fertilization in a considerable number of species belonging to this 

 order. He classifies them from this point of view as follows: — 

 I. Monoclinous species. (A) with dichogamous (proterandrous) 

 flowers ; (B) with synacmic flowers. II. Diclinous flowers. In 

 each class are a number of subdivisions. 



Division of the Nucleus, § — For the purpose of endeavouring to 

 reconcile the description of the mode of indirect division of the cell- 

 nucleus given by Strasburger in the case of plants, and by Flemming 



* Nature, xxviii. (1S83) p. 81. 

 t Ber. Deutscli. Bot. Gesellsch., i. (1883) pp. 165-9. 

 j Jabrb. Bot. Gait. Berlin, ii. See Science, ii. (1883) pp. 53-4. 

 § Comptes Eundus, xcvii. (1883) pp. 646-8. Of. ibis Journal, i. (1881) 

 p. 621 ; ii. (1882) p. 317. 



