452 MR: J. R. GREEN ON THE ORGANS OF 
mesophyll of the leaf. If the chlorophyll be removed from 
these overlying mesophyll-cells, by the action of alcohol or other 
solvent, the translucent specks appear. Their position in the 
leaf in these species contradicts a statement made by Unger *, 
that only in Myoporium tuberculatum do oil-secreting glands 
occur as a rule in the midst of the leaf-tissue. Such bodies 
appear therefore to be present throughout the genus Hypericum 
(compare figs. 12 and 14, Pl. XXXIX.). They are distributed 
over leaves, braets, and sepals, and in some species, as in 
H. balearicum, over certain parts of the stem. 
Taking the Order throughout, four distinct kinds of secreting- 
organs are to be found, but not necessarily all in one plant, for 
certain of them are absent from some species. The most promi- 
nent of them are the pellucid dots referred to as chiefly cha- 
racteristic of the leaves. These dots are hollow cavities, more 
or less spherical in shape. They extend, in the thinner-leaved 
species (as H. perforatum, H. tetrapterum, &c.), throughout the 
whole width of the mesophyll of the leaves, and hence touch 
the epidermis at both surfaces (fig. 12). In the thicker-leaved 
species (H. calycinum, &c.) they are imbedded more deeply 
in the tissue, and encroach on only part of the mesophyll 
(fig. 14). Their situation, and the consequent fact that they 
are covered by layers of cells containing chlorophyll, account 
for their apparent absence when the leaf is looked at before 
treatment with a solvent of the colouring-matter. 
These hollow cavities contain in all cases ethereal oil, the 
escape of which, on the rupture of the epidermis over the reser- 
voir, causes the fragrance alluded to. 
The second kind of secreting-organ is to be found in the 
petals, sepals, and fruits, and in the stems of the different 
species. From the stems of some species, such as H. balearicum, 
these bodies are absent, being replaced by reservoirs that may be 
included in the first class. In stems that have not the spherical 
reservoirs, these organs of the second kind are abundant. They 
take the form of true resin-passages, which occur in the cortex 
and the pith, but are not found in the fibrovascular system. 
They are rather differently distributed in the stem and in the 
fruit, and their course is different in the two regions. In cylin- 
drical stems they are generally disposed in a single row in the 
cortex, some few layers of cells below the epidermis, and they 
* * Anatomie und Physiologie der Pflanzen,’ p. 213. | 
