SCOTS PINE. 377 



526. Male Cone (General Characters). Examine 

 the male cones which are seen on some of the elongating 

 shoots, a number of them being grouped together at the 

 base of the shoot. Note that each male cone arises in the 

 axil of a scale-leaf, is ovoid and about 6 to 8 mm. long, and 

 consists of an axis bearing a few basal scales and the 

 numerous spirally arranged yellow stamens ; each stamen 

 consists of a very short filament and a flat scale-like 

 anther ; the anther ends in a narrow upturned crest and 

 bears on its underside two pollen-sacs lying side by side. 

 Since the male cones are aggregated at the base of the 

 shoot, and fall off after the pollen has been shed, the stem 

 is left bare in this region look for twigs with successive 

 bare patches formed in this way, alternating with zones 

 bearing the dwarf -shoots and ordinary branches. 



527. Longitudinal Sections of Male Cone. To 



study the development of the pollen-grains, male cones 

 should be put into alcohol at intervals during spring, and 

 the pollen-sacs teased out in water or glycerine on a slide. 



In a radial longitudinal section of a cone taken 

 about end of May note the axis, with vascular bundles 

 giving off a single bundle to each of the stamens ; each 

 stamen shows on its underside one of the two pollen- sacs, 

 and ends in an upturned crest. 



Cut a tangential longitudinal section of the male 

 cone ; the stamens will be cut transversely, and the sec- 

 tions will fall away in one of these sections, note (1) the 

 two ripe pollen-sacs are separated by a vertical partition 

 consisting of a few layers of collapsed cells ; (2) this 

 partition is thickened above and below, so as to be I- 

 shaped in section, and in the tissue of the upper thickening 

 there is embedded the small vascular bundle ; (3) the 

 whole stamen is covered by an epidermis layer, which is 

 produced on the flank of each pollen- sac into a narrow 

 wing; (4) along the lower side of each pollen-sac the 

 epidermal cells are very small, diminishing in size on either 

 side of the dehiscence-line ; (5) within the epidermis, 

 the cavity of each pollen- sac is lined by a few layers of 

 flattened cells, 



