1887.] Mr W. Gardiner, On the petiolar glands of the Ipomeas, 83 
was shown to be of a watery nature, and to possess a slightly acid 
reaction. ‘The function performed by the hairs and their secretion 
was at the time uncertain. The author of the present paper 
believes that the secretion serves to attract ants, which besides 
feeding upon it, also protect the thin young climbing shoots by 
attacking and destroying other creeping insects of alien race with 
whom they may meet in their passage up and down the stem. 
Many of these insects such as cockroaches and caterpillars are 
known to be very destructive to young buds. The author has 
been able to establish from actual observation of plants at Kew, 
that ants actually visit the hairs and feed upon the secretion. 
Similar hairs are found upon the calyx. In a certain unnamed 
species of Combretum sent by Ernst from Caracas hairs of essen- 
tially the same structure were also observed. 
(4) On the petiolar glands of the Ipomeas. By WALTER 
GARDINER, M.A. 
In all the species of Ipomcea which were examined, secretory 
structures probably of the nature of extra-floral nectaries were 
observed. A pair of such glands are found in each leaf; one 
on either side of the petiole at the point of junction of the petiole 
and lamina. The leaves of Ipomcea Horsfalli possess glands of an 
especially simple structure while those of Ipomcea paniculata 
exhibit a distinctly complex organisation resembling in fact a 
racemose gland and possessing a well developed duct. Other 
species present gradations between these two extremes. The 
secretion arises from capitate hairs which are either situated singly 
at the bottom of a depression of the epidermis, or in numbers line 
a saccate or racemose involution of the same. The author believes 
that the secretion of these petiolar glands attracts ants, which 
in their turn serve to protect the plant. 
(5) On the occurrence of secreting glandular organs on the 
leaves of some Aroids. By WALTER GARDINER, M.A. 
The author remarked that it has been frequently stated that 
the entire absence of all extra-floral secretory structures in Mono- 
cotyledonous plants furnishes one of the most striking points of 
difference between the above-named group and the Dicotyledons. 
One would be led to expect however that some form of secretive 
_organ should be present, and that probably they would be found— 
if anywhere—among the Aroids. Guided by these considerations 
the author made a careful examination of the Aroids at Kew, and 
was so fortunate as to find two individuals, viz. Aglaonema Mannii 
and Alocasia cuprea, which appear to him to possess definite organs 
of secretion. The structure of these organs was then shortly 
