THE AMERICAN BOTANIST. 
109 
Many of the Euphorbiace^ are provided with extra- 
floral nectar glands which have been noticed by systemat- 
ists as well as physiological botanists. They are found 
on the stipules of Jatropa nlulti^ida and on the petiole at 
the base of the leaf-blade of Aleurites molluccana. In a 
paper by Percy Groom on the extra-floral nectaries of the 
allied Aleurites cordata these petiolar nectaries are de- 
scribed as follows : 
**Each nectary is a green-stalked, shallow basin, the 
concavity of which is tinted red. The secreting cells which 
line the basin form a single layer of palisade-like cells. The 
general culticle is preserved over these and the secretion 
emerges through splits in it. The secreting cells contain 
proteids, sugar, a red coloring matter (a compound of 
tannin?), tannin but no starch. In the ground paren- 
chyma starch tannin and crystals of calcic oxalate occur . 
The conducting parenchyma contains sugar but no starch 
or cr3^stals. Darkening the nectaries of leaves on the 
plant, or of excised leaves, or darkening the whole leaves, 
caused a gradual disappearance of the starch, but the 
nectaries continued to excrete for some time." Among the 
Malvaceae growing in Guam several are provided with 
nectar-glands on the underside of the midrib. These are 
most conspicuous in Urena sinuata occurring not only on 
the midrib but sometimes on the main lateral ribs of the 
palmate leaves. They also occur on all leaves of cotton 
{Gossypium sp.) and on the midrib of Pariti tiliaceum in 
the form of vaginate glands. 
The sweet fluid secreted by these glands is eagerly 
sought by sugar-loving insects and a number of authors 
maintain that the power of secreting it has been specially 
gained by plants for the sake of attracting ants and wasps 
which will serve as defenders against caterpillars, leaf- 
cutting insects or other enemies; but Darwin, after a 
series of observations, could not see any reason to believe 
this to be so wnth the species observed by him, although 
the fact that these glands are visited by insects for the 
sake of their nectar can be verified at any time of da}^ 
