228 PHARMACEUTICAL BOTANY 
Gymnosperms. In Monocotyledons the single cotyledon is a 
terminal structure and truly axial in relation to the hypocotyl 
and radicle. From a primitively Monocotyl-like ancestry 
Dicotyledons develop a second cotyledon on the epicotyledonary 
node. Later, by a suppression of the second node the second 
cotyledon is brought to the level of the first. 
Scate Leaves.—Scale leaves are reduced foliage leaves. 
They are found on certain rhizomes, above ground stems, such 
as Dodder, Indian Pipe, etc., on bulbs, and forming the pro- 
tective scales of scaly buds. 
Surface View Section 
Fic. 157.—The growing end of the stem of the aquatic plant, Elodea canadensis, 
showing the origin of leaves. The larger over-lapping leaves are omitted. A, sur- 
face view; B, in section. (Courtesy of Standard Scientific Corp., formerly Scientific 
Equipment Dept. of Kny-Scheerer Corp.) 
Fouace Leaves.—These are the common green leaves so 
familiar to all. 
Bracr Leaves are modified leaves appearing on inflorescence 
axes. 
SEPALS, PETALS, MICROSPOROPHYLLS and MEGASPOROPHYLLS 
are floral leaves and will be treated at length under the subject 
of the flower. 
Oricin AND DeveLopMEnt or Leaves.—Leaves arise around 
the growing apex region of a stem or branch as lateral outgrowths, 
each consisting at first of a mass of cells called the primordial leaf. 
Through continued cell-division and differentiation of these cells 
