T1IK AXTHKR. 



283 



nature, or line of dehiscence, by which the anther opens at maturity 

 tO'disclmrge the pollen (Fig. 473). This line is for the most part 

 exactly lateral in innate anthers ; but it looks more or less evidently, 

 and often directly, inward in introrse, and outward in extrorse 

 anthers. In certain eases the cells of the anther open only at the 

 summit, by a pore or hole, as in Py- 

 rola (Fig. 474) and most Ericaeeous 

 plants. In the Whortleberry family 

 each cell or lobe is commonly pro- 

 longed into a tube, which opens only 

 at the apex ( Fig. 391). In the Bar- 

 berry (Fig. 475), and in nearly all 

 plants of the Barberry family, the 

 whole face of each anther-cell sepa- 473 m 473 



rates by a continuous line, forming a kind of door, which is attached 

 at the top, and turns back, as if on a hinge : in this case the anthers 

 are said to open by valves. In the Sassafras (Fig. 1114), and many 

 olher plants of the Laurel family, each lobe of the anther opens by 

 two such valves, like trap-doors. 



527. Sometimes the anthers are one-celled by the suppression of 

 one lobe, being dimidiate, or reduced as it were to half-stamens, as 



in Gomphrena or Globe-Amaranth (Fig. 478). 

 But most one-celled anthers are the result of 

 the confluence of the two cells into one. A 

 comparison of the two-celled anther of Pent- 

 stemon pubescens, where the two cells diverge 

 below and are somewhat united at the top 

 (Fig. 47G) with the kidney-shaped one-celled 

 anther of a Mallow, opening by a continuous 

 line all round the margin (Fig. 477), shows 

 how this result is brought about. 



528. As to anatomical structure, each lobe of the full-grown 

 anther consists of an epidermal membrane, lined with a delicate 

 fibrous tissue, and surrounding a cavity filled with pollen. This 



FTG 473. A stamen, with its anther, 6. opening in the normal manner down the whole 

 length of the outer side of each cell : a, the filament 



FIG. 474 Stamen of a P) rolu. ; each cell of the anther opening by a terminal orifice. 



FIG. 475. Stamen of a Barberry ; the cells of the anther opening by an uplifted valve. 



FIG. 476 A stamen of rentstemon pubescens ; anther-cells slightly confluent 



FIG. 477. Stamen of Mallow ; the two cells confluent into one, opening round tho margin. 



FIG 478. Antlier of Globe Amaranth, of only oce cell ; the other cell obliterated. 



