THE GYMNOSPERMS 93 
Note the scale leaves appearing on the stem in the younger 
growth, and as sheaths about the bases of the needle leaves. 
Remove one group of needle leaves, and after taking the 
sheath away see how the pair or group of leaves is arranged 
at the base. Sketch such a group. Is there any regularity 
in the way the different groups of needle leaves are arranged 
on the branch? 
Observe the hardness and toughness of the leaves. Make 
a thin cross-section of one, and note the following regions: 
(1) The heavy epidermal and strengthening regions. How 
many layers of cells? Where most numerous? (2) The 
chlorophyll-bearing tissue, in which are the resin-ducts defi- 
nitely bounded by wall-cells. (3) The central light-colored 
pith region, bounded by a definite sheath of cells. (4) 
Within the pith region two groups of conducting cells—the 
vascular bundles. 
What assists this leaf in persisting through the severe 
winter weather? Does the resinous matter have anything 
to do with this protection? 
ReproductionIn the ferns the sporangia are borne 
sometimes on chlorophyll-bearing leaves and sometimes on 
specialized spore-bearing leaves, while in Spermatophytes 
they are usually borne on specialized leaves—sporophylls— 
and these are grouped in cones or clusters. The pines have 
two distinct kinds of cones—those producing sporangia that 
contain small spores, and those producing sporangia that 
contain large spores. 
a. The cone bearing the small spores is called the stami- 
nate cone, and each sporophyll is a stamen. The spores are 
usually mature in May or June. Study material collected 
just before the spores are ripe. 
Sketch the cone, showing the outside appearance and 
arrangement of the sporophylls that compose it. Are cones 
borne separately or in clusters? Remove one or two sporo- 
phylls (stamens) and sketch, showing the very short stalk, 
