THE ANTHEK. 



283 



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

 to discharge the pollen (Fig. 473). This line is for the most pai-t 

 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 cases the cells of the anther open only at the 

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

 rola (Fig. 474) and most Ericaceous 

 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 BarbeiTy family, the 

 whole face of each anther-ceU sepa- 

 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 

 other 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. 476) 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 



FIG. 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 Pyrola ; 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 Pentstemon pubescens ; anther-cells slightly confluent. 



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



FIG. 478. Anther of Globe Amaranth, of only one cell ; the other cell obliterated. 



