28 BOTANY. 
adhere to a greater or less extent; sometimes this takes between an entire 
whorl, so as to form a tube; the stamens are then monadelphous. They are 
diadelphous when forming two bundles, triadelphouws when united into three, 
and polyadelphous when grouped into a greater number. Filaments are 
sometimes united with the pistil to form a colwmna or column, as in Asclepias. 
The column is called gynostemium, and the flowers are said to be gynan- 
drous. 
The ANTHER corresponds to the blade of the leaf, and consists of lobes with 
cavities inclosing a fine powder called pollen, which, when mature, is dis- 
charged by an aperture. The covering of the anther is double; the outer is 
called exothecitum, the inner endothecitum. The anther usually possesses two 
lobes, corresponding to the two halves of the leaf; in each lobe there are 
generally two cavities separated by the septum. The connective divides the 
two lobes. An anther with four persistent cavities is called guadrilocular or 
tetrathecal. When, as is more generally the case, the septa are absorbed, the 
anther becomes bilocular ur dithecal. Sometimes there is but one cavity, con- 
stituting the wnilocular or monothecal anther. The form of the anther lobes 
varies much in different plants ; more usually they are oval or elliptical. The 
part of the anther to which the filament is attached is called the back, the 
opposite being the face. The division between the lobes is marked on the 
face of the anther by a groove or furrow, and on the face there is usually a 
suture, along which the pollen is discharged. When the filament appears to 
be continued along the back of the anther, this is adnate or adherent ; innate 
or erect when it ends at the base. A versatile anther is one which is not 
fixed immovably to the filament. Sometimes the connective is more or less 
horizontal, and bears a lobe of the anther at each end; it is then said to be 
distractile. The opening of anthers to discharge the pollen is their dehis- 
cence. This may be either longitudinal or transverse. In circwmscissile 
dehiscence, the entire apex of the anther comes off to permit the escape of the 
pollen. An anther is introrse when it opens on the surface next to the centre 
of the flower, and ertrorse when the contrary takes place. A stamen some- 
times degenerates and becomes sterile from the absence of a proper anther ; 
such are called staminodia, and may present various appearances, as scales, 
leaves, petals, &c. 
We have already referred to the adhesion of the filaments of the stamen 
leaving the anthers free. These in turn may be attached without involving 
any connexion between the filaments. In this case the flower is said to be 
syngenesious or synantherous. Stamens whose length does not exceed that 
of the tube of the carolla are said to be included ; they are exserted when of 
greater length. 
Although the stamens are usually of the same length, yet it often happens 
that one or more is longer than the rest. Flowers are didynamous when, of 
four stamens, two are long and two are short. When there are two pairs of 
long stamens separated by a pair of shorter, the flower is ¢etradynamous. A 
stamen is said to be declinate when it bends to one side. 
Potten, or the powdery matter discharged from the anther, consists of 
small independent cells which have been developed in the anther by the 
28 
