ON THE PINES UF AUSTRALIA. 153 
bearing surfaces are practically hidden, and cover too 
small an area to characterise the tree when so exposed. 
In this contention of ours, i.e., accounting for the con- 
crescence in Callitris and the functions of the conical 
epidermal cells and probable movement of the ventral sur- 
face, the following quotation, we think, rather strengthens 
our views. In the case of Picea halepensis “‘the leaves 
of this tree in warm sunny weather are fully separated, 
but if the sky became overcast they close partially; the 
sirocco produces a similar but more marked effect, but in 
rain the leaves collapse giving the tree a most melancholy 
aspect.’’* 
Resin Cavities or Oil Glands.— When present these bodies 
are found to be situated in the upper portion of the con- 
crescence and in the middle of the leaf substance. They 
are fusiform in shape, (Fig. 14) and a cross section showing 
a circle or an ellipse Figs. 7 to 9, and their limited length 
bars them from being classified as canals—a term used in 
describing identical bodies in other Conifers. To be more 
exact they occur inthe centre of the spongy tissue and are 
not regularly distributed, sometimes one, and even two 
figures will be found in each leaf, whilst often only one 
or two of the sections may contain one. The glands or 
cavities are all lined with secretory cells, and may be 
classed as lysigenous. Under such circumstances no assist- 
ance was rendered by these for diagnostic purposes, as 
obtains in other Conifers, and cannot be used in a manner 
employed by Hngelmann, who grouped the species of Pinus 
according to the position of their ducts. He also lays 
stress in the circumstance of the resin canals being sur- 
rounded by strengthening cells or devoid of such investment. 
These remarks, however, cannot be applied to Callitris as 
far as our observations go. 
* Moggridge, Journ. of Bot., Feb. 1, 1867. 
