278 PHARMACEUTICAL BOTANY 
time of dehiscence. Again, in various species of Laurace@, the 
anthers remain four lobed and dehisce by four recurved lids. 
But in the great majority of Angiosperms each pair of pollen 
sacs fuse before dehiscence, owing to the breaking down of the 
partition between them, and so, at that time, show two-celled 
anthers. Still more rarely the anthers may be two-celled in 
their young state and by the breaking down of the partition 
become one-celled, e¢.g., Malvaceae. 
. - ex 
Connective 
a ed 
5. 
ms —_ 
Stomium — 
Pollen Mother ae 
Cell a Gate, he Ae 
Tapetum= ~ 
Fic. 195.—Cross section of immature anther of Johnson grass (Holcus halepensis 
L.). The pollenm other cells are contained within four microsporangia. x, 
exothecium. (Mottier.) 
Externally the mature anther is bounded by an ExoTHECIUM 
or epidermis, often swollen, where lines of dehiscence occur, 
which may develop stomata, also hairs. Within it is a combined 
layer or set of one to often two or three, sometimes five or six 
cell layers (Agave, etc.) of indusial and sporangial cells, the 
EnpoTHECIUM. The outermost one to three layers of this 
become spirally, annularly or stellately thickened to form the 
elastic tissue of the anther, which, by pressure against the delicate 
epidermis or ExorHecrum, causes ultimate rupture of the anther 
wall. Within the innermost endothecial layer, bounding each 
sporangium, is the Tapetum, a single-celled layer. This, near 
the time of dehiscence, undergoes breaking down or absorption 
