_ 246 : MODIFICATIONS OF THE ANTHER. 
more commonly the case, the partitions separating the two loculi 
of each anther-lobe become absorbed, it is two-celled or bilocular 
(fig. 536). In rare cases, the anther is wiilocular or one-celled, 
as in the Mallow (jig. 535), Milkwort (jig. 515), and Lady’s 
Mantle (fig. 516): this arises either from the abortion of one lobe 
of the anther, and the absorption of the septum between the two 
cells of the lobe that is left ; or by the destruction of the partition 
wall of the two lobes as well as of the septa between the cells of 
each lobe. In some plants, again, as in many species of Salvia, 
the connective becomes elongated into a kind of stalk, each 
end of which bears an anther lobe (fig. 517), in which case there 
appear to be two wnilocular or one-celled anthers. When this 
occurs one lobe only, lf, contains pollen; the other, ls, is sterile. 
That surface of the anther to which the connective is attached 
is called the back (fig. 513, a), and the opposite surface, B, B, is 
the face. The latter always presents a more-or less grooved ap- 
pearance (figs. 513 and 518, ¢), indicating the point of junction 
of the two lobes. Each lobe also commonly presents a more or 
less evident furrow (fig. 518, b), indicating the point at which the 
mature anther will open to discharge the pollen ; this furrow is 
termed the suture. By these furrows the face of the anther may 
be generally distinguished from the back, which is commonly 
smooth (fig. 513, a), and has moreover the filament attached to 
it. The face is generally turned towards the gynoecium or centre 
of the flower, as in the Water-lily (jig. 522), Vine (fig. 518), 
and Tulip (fig. 528), in which case the anther is called introrse ; 
but in some instances, as in the Iris, and Meadow Saffron (jig. 
519), the face is directed towards the petals or circumference of 
the flower, when the anther is said to be extrorse. 
Its Development and Structure.—When first formed the an- 
ther consists of parenchymatous cells of about the same size 
and form; but ultimately each lobe presents two central masses 
of cells which are termed parent or mother-cells, from being de- 
voted to the formation of the pollen (fig. 520, em), and over which 
we have three distinct layers of cells. The inner one, el,—that 
is the layer immediately enclosing each central mass, is called the 
endothecium or tapetum ; it is formed of but a single row of deli- 
cate cells, which appear to contain nitrogenous matter, and sup- 
posed to be concerned in the nourishment of the pollen-cells in 
their early growth. This layer commonly disappears as the 
pollen becomes matured, but it is persistent in those anthers 
which have porous dehiscence. The layer, ci, immediately out- 
side the endothecium, is termed the mesotheciwm. It is a per- 
manent layer, and consists of one or more rows of cells, some of 
which, except in the case of anthers opening by pores, contain 
spiral, reticulated, or annularly arranged fibres. The third or 
external layer, ce, is of an epidermal nature, with a well-marked 
cuticle, and is called the exothecium, and upon which stomata are 
frequently found. 
