2 ART. 3. — K. ONO. 



the fact that ants are attracted by that organ, which circumstance 

 tends to protect the plants from the injuries caused by the 

 larva of certain insects. It has also been observed that even 

 Hymenoptera are attracted by the nectaries. In tropical lands, 

 the relation between ants and plants^^ is especially remarkable. 

 As to the physiology of extranuptial nectaries, Bonnier^^ and 

 Morini^^ may be mentioned as the first two early writers, who 

 made investigations on the contents of the nectaries. They did 

 not, however, show how sugar is formed in the nectary. 



It is owing to Wilson's^^ researches, that we now know 

 the cause of the secretion to be the local osmotic pressure, pro- 

 duced by the storage of sugar solutions in the tissues of the 

 nectaries. Recently Haupt"^ carried on physiological experiments 

 concerning the secretion of the nectary, and estimated the influence 

 of warmth, moisture and sunlight on the secretory phenomena. 

 He observed also the resorption of nectar in Vicia faba. 



Lastly, on the development of extranuj)tial nectaries in 

 general, we have had hitherto very few investigations, of which 

 Correns"'^ paper on the Dioscorea-nectâries is worthy of mention. 



AVith a view of throwing some light on the anatomy and phy- 

 siology of extranuptial nectaries,^^ I have worked under the guidance 

 of Prof. Miyoshi, during the academic year of 1904-1905, 



1) Schimper. Die AVechselbeziehungen zwischen Pflanzen und Ameisen im tropischen 

 America. .Jena, 1888. 



2) Bonnier. Les nectaires. Étude critique, anatomique et physiologique. Bull, de la 

 soc. bot. de France. ï. XXV, p. 262. 1878. 



3) Mo ri ni. 1. c. 



4) Wilson. The causes of the excretion of water on the surface of nectaries. 

 Untersuch, a. d. bot. Inst, in Tübingen. Bd. I, p. 8. 1881. 



5) Haupt. Zur Sekretionsmechanik der extrafloralen Nektarien. Flora. Bd. 90, p. 1. 1902. 



6) Correns. Zur Anatomie und Entwickelungsgeschichte der extranuptialen Nektarien 

 in Dioscorea. Sitzungsb. d. k. k. Akad. d. Wiss. Bd. 97, Theil I, p. 561. Wien, 1888, 



7) I use the term "extranuptial nectary" in the same sense, as did Knut h in his 

 ' Bliithenbiologie. " 



