AC ACT A SPIIJEttOCEPIIALA AND CECltOPTA PELT AT A. 407 



menced a habit of visiting, and probably of protecting, the tree 

 when the glands were in an excretory stage of development ; for 

 we know that the nectar-glands on Passion-flowers, according to 

 Mr. Belt*, serve to attract the small black ants who guard the 

 tree from other creatures. 





Appendix. — On the Nectar-glands of the Common Brake Fern 



(Pteeis Aquilina). 



Since reading the paper to which the present remarks are ap- 

 pended, an observation has been made which, apart from some 

 interest of its own, has a direct bearing on my views as to the 

 origin of food-bodies. 



On June 5th I noticed the presence of smooth green promi- 

 nences at the base of the fronds of the common Brake Fern. 

 Further examination showed them to be secreting glands, produ- 

 cing a sweetish fluid which exudes from their surfaces. The 

 glands are busily visited by more than one kind of ant, especially 

 by Myrrnica ; they are also attractive to Elater and another 

 kind of beetle. The gland is well developed while the fern is 

 still very young, and it ceases to secrete when the plant becomes 

 mature. The glands are shown in fig. 6 at g g, the latter 

 being merely seen in profile. In the young state the gland is a 

 fairly conspicuous triangular prominence, standing out clearly 

 from the pubescent surface of the plant. As each frond is fully 

 developed, the gland at its base becomes gradually flattened, and 

 ceases to be so conspicuous. I have not yet been able to examine 

 the minute structure of the glands. 



The glands have a remarkable power of secreting rapidly. The 

 following observations on this point were made by my father. 



June 8th. "Examined several ferns with Myrrnica on them, 

 and found the glands quite dry. Brushed off the ants, and in 

 from 5 to 6 minutes distinct drops of secretion were formed." On 

 the same day he repeated the observation, and found that the drops 

 of secretion were, as before, reproduced in 6 minutes. 



The method adopted by the ants to obtain the nectar is in ac- 

 cordance with this high rate of secretion ; they may usually be 

 found seated patiently on the glands, evidently sucking up the 

 secretion at fast as it is produced. In many glands shallow exca- 

 vations are found which appear to have been gnawed ; and this is 

 probably the work of the ants. If this be so, it has an interesting 



* Loc. rit. p. 224. 



