156 TYPE STUDIES 



the branches. Compare their size and texture with the car- 

 pellate cones at the time of pollination. Draw a side view of 

 the cone, if time permits, and then detach a scale and draw 

 two views as described in (t, 2, 3, noting and comparing the 

 relative position of the structures described there. 

 I. The two-year-old carpellate cone and its scales. Search for 

 two-year-old cones, establishing their identity by their posi- 

 tion on the branches. Compare their size and texture with 

 the year-old cones and the cones at the time of pollination. 



1. Draw a side view, if time permits. 



2. Cut into the cone with a heavy knife, carefully detaching 

 one of the scales. Draw the scale as viewed from the inner 

 face, noting (a) that the ovules are ripening into winged 

 seeds, the wings developing from a tissue that separates 

 from the inner face of the scale ; (h) the relative position 

 of the point, above and between the maturing seeds. 



3. Draw a side view of the cone scale to show the position 

 of the bract in the axil of which the cone scale is borne 

 and the relation of parts in comparison with the cone scale 

 at the time of pollination. 



J. The ovule on the year-old cone. Sections of the ovule on 

 the scales from a year-old cone may be cut free-hand, but 

 stained microtome sections are much more satisfactory (Sec. 

 212). They should be cut lengthwise of the ovule and per- 

 pendicular to the surface of the scale. Observe : 



1. The enveloping integument meeting at the tip of the ovule 

 where there was formerly an opening, the micropyle, at 

 the time of pollination. 



2. Within the integument and below the micropyle the 

 pollen chamber in which germinated pollen grains may be 

 found sending their tubes into the interior of the ovule. 



3. A conical structure, the nucellus, into which the pollen 

 tubes have grown, lying within the integument. 



4. A large area in the interior of the nucellus, called the 

 embryo sac, which contains a delicate tissue, endosperm, 



