404 ME. F. DARWIN ON THE GLANDULAR BODIES ON 



The nectar-gland. — The gland which secretes the nectar is 

 situated at the base of the petiole ; in form it somewhat resembles 

 a flat thorn, such as those on roses with the top cut off. The 

 gland is shown in g g in fig. 1. Its profile outline is there seen 

 to be something like that of a volcanic mountain ; and it very 

 well deserves the name of " crater-formed " gland, applied to it by 

 Mr. Belt. The crater is a long narrow trough running along the 

 ridge-like summit of the gland ; and into this trough the nectar 

 wells up from the subjacent secreting tissue ; in my plant the 

 secretion was so abundant as to drip on to the floor of the hot- 

 house. The gland, which projects about 2 millims. above the sur- 

 face of the petiole, has a curious look of having been thrust into a 

 cleft in the stalk of the leaf ; this arises from the fact that the 

 stalk is traversed by a longitudinal groove, and that it is from the 

 base of this groove that the gland arises as an excrescence ; and 

 as it grows up between the walls of the groove, it seems to come 

 through a split in the petiole. 



In transverse sections perpendicular to the axis of the petiole 

 it may be seen that the epidermis of the gland is continuous with 

 that of the stalk, also that fibro-vascular bundles run up on each 

 side of the central mass of glandular tissue. The latter is flask- 

 shaped in transverse section, the neck terminating above in the 

 crater, and the body resting on the upper surface of the petiole. 

 The glandular tissue is made of loose elongated cells, which are bi- 

 laterally symmetrical about a central line, from which they radiate 

 outwards and downwards. 



Cecropja peltata (the Imbauba tree) .—I have already quoted 

 enough from Fritz M tiller's interesting paper to explain the rela- 

 tions existing between this tree and its army of ants. The fol- 

 lowing is his account of the food-bodies. At the base of the leat- 



millim 



W 



undmg 



parts, and embraces fully one half of the leaf-stalk. 



brown 



This cushion 



young 



branches. As the leaf develops, the cushion appears as a white 



unicellular 



utnumber 



simple ones. The former attain a length of 1 millim., and consist 

 of about twelve cells, the lower ones being cylindrical, the upper 

 spherical or egg-shaped, giving a moniliform appearance to the hair, 



