NOTES ON ACACIA. 467 



He adds that there is no evidence that the insect is a 

 symbiont by virtue of any protection it affords. He con- 

 cludes that these organs perform excretory functions, and 

 that they are not, in his opinion, strictly speaking, glands 

 or nectaries. He suggests the name "vents" for them. 

 44 In the phyllode they are mere relics— not yet altogether, 

 but almost obliterated, and now functionless." 



There is a valuable paper, 1 with excellent illustrations, 

 of nectaries on both petiole and leaf, the illustrations chosen 

 being those of the Cherry leaf and its petiole. Commencing 

 With references to floral nectaries, the author passes on to 

 a brief sketch of the literature of extra-floral nectaries, 

 touching on the work of Belt and Delpino. He points out 

 that microscopical examination of these organs at various 

 stages shows that their development takes quite different 

 courses in different species, and there seems no single 

 underlying principle governing their appearance. Their 

 secretions also vary widely, or they may be absent. 



The idea that the presence of these nectaries is to divert 

 the attention of ants from the richer nectaries in the flowers 

 themselves (baits to insects engaged in the work of pollin- 

 ation) appears to have little basis in fact as far as obser- 

 vation goes. 



It is also pointed out that in some of the broad-beans 

 (Vicia), it has been found that bees visit the extra-floral 

 nectaries in preference to those in the flower. 



But, speaking generally, the conclusion of the anonymous 

 author is that extra-floral nectaries must be looked upon 

 as little better than accidents in the development of the 

 plant ; they may of course have been more useful at some 

 earlier stage in the plant's evolutionary history, but at 

 present we can hardly avoid the conclusion, in many cases, 



1 " Extra-floral Nectaries," Journal of Heredity, August, 1915, p. 367. 



