614 DR. M. T. MASTERS ON THE PASSIFLORACEA. 
an ordinary stoma, between the side of this solitary sphincter-cell and the adjoining 
epidermal cell. I have not myself seen these half stomata, probably because my obser- 
vations have not been sufficiently extended. 
Beneath the outer epidermis are three or four rows of spheroidal cells containing 
chlorophyll. Within this (in P. alata) there is a quantity of loose spongy cellular tissue, 
consisting of irregularly branching cells, between whose subdivisions are left large spaces 
or lacune. These cells contain little or no chlorophyll. Traversing this tissue are 
numerous bundles of slender spiral vessels. The inner epidermis consists of flattened 
polygonal cells with oval stomata. 
Petals.—The outer or lower epidermis of the petals of P. alata consists of one layer of 
thickened, somewhat polygonal, seareely sinuous cells, beneath which are numerous 
globular cells closely packed, except towards the inner surface, where there are a few 
lacunæ. The spiral vessels are of the same character as in the sepals. The inner epi- 
dermis consists, in the basal portion, of flattened cells ; but above, where the petal becomes 
eoloured, papular cells make their appearance. 
The epidermis of the petals in the hybrid x P. ceruleo-racemosa consists also of sinuous 
cells, and this on both surfaces. It is perforated by few or no stomata. The colouring- 
matter is of a fluid nature, and is contained in the cells subjacent to the epidermis. 
Corona.—A section through one of the larger rays in P. alata showed several bundles 
of spiral vessels traversing a quantity of cellular tissue, the outermost cells of which were 
. filled with red colouring-matter. The epidermal cells are cuboidal in section, and either 
flat on the outer surface, or, in other cases, prolonged into conical points. There is pro- 
bably some relation between the presence of this form of cellular tissue and colouring- 
matter or other secretion, since it is sometimes present, sometimes absent, both from the 
surface of the petals and from the rays of the corona*. — 
With reference to the spiral vessels by which the rays of the corona are traversed, I 
may remark that, while in the case of the larger rays there are sometimes several 
bundles in each, in the smaller rays there is only a single vessel; but not one, however 
small, seems to be destitute of its vessel. It is worth remembering this, as some 
stress is laid in certain cases, e. g. in Orchids, on the number and disposition of the spiral 
vessels as indicative of so many distinct, or potentially distinct, organs. It would surely 
not be correct to assume, from the presence of two or more bundles of vessels in one 
thread of the corona of a Passion-flower, that such thread is really of composite nature. 
The annular rim which projects from the inner surface of the flower-tube below the 
* opereulum ” consists of a mass of globular cells, covered by a papular epidermis, and 
traversed by a solitary bundle of spiral vessels. In some of the cells may be seen con- 
glomerate raphides. 
Stamens.—The filaments present an epidermis of squarish thick-walled cells, destitute 
of stomata, enclosing cellular tissue of closely packed, oblong, cylindrical cells, enclosing 
cA opel bundle of fine n vessels. The disposition of the tissues in the excurrent 
po cR call attention to Mr. Tuffen West's remark in the Journal of Microscopical Science, 1859, p. 1, t. 1, 
as to ho efc of this vero-pile-ie suo in giving “air” ond a transparent fat to coloured surfaces 
