352 MORPHOLOGY. 



spaces, filled with air, which gives them a snow-white appearance. 

 The appendages of the filament and the connective exhibit like 

 characters. A simple vascular bundle usually runs through the 

 filament and the connective ; but not unfrequently the vessels are 

 wanting, as in the case of the Amarantacea. The vascular bundles 

 are never ramified, excepting in the case of the lobed or pinnate 

 stamens, and then a bundle enters each lobe. The epidermis is 

 here, as in the petals, an intermediate structure between epidermis 

 and epithelium; it presents sometimes, though seldom, stomates, 

 and frequently regular, elegant, and partially brightly coloured 

 hairs. 



In the Apocynacece, a little group of hairs is exhibited beneath 

 the anther, upon the upper surface of the filament, in which a quan- 

 tity of viscid matter is secreted, so that by these adhesive tufts of 

 hair the stamens adhere firmly to the large stigmatic body, and 

 thus render spontaneous fertilisation impossible, since the surface 

 destined to receive the pollen is below the point where the stamens 

 and stigmatic body are connected. The anthers also sometimes 

 secrete a viscid substance, by means of which they adhere amongst 

 themselves, as in the Composites (here it is perhaps formed by the 

 solution of the secreted layer of epidermis), or they cleave to the 

 body of the stigma, as happens in some of the Apocynacea. 



The development of the epidermis into surfaces secreting nectar 

 is also frequent here, especially on the appendages at the bottom of 

 concave forms, at the points of the stipules of the Lauracea, &c. 



Far more important is the structure of the anther. Originally 

 this is formed of quite uniform, delicate-walled cellular tissue ; 

 soon, however, after the loculi become externally characterised as 

 incipient expansions, two layers may be distinguished in the 

 cellular tissue, namely, that which is destined to form the walls of 

 the thecae, and that which is appropriated to the formation of the 

 parent-cells of the pollen. Between these exists another thin layer 

 of cells, which at the time of the perfect formation of the pollen 

 becomes dissolved and absorbed, so as to ensure for the pollen the 

 free space requisite. In all three layers a constant development of 

 cells within cells goes on until the completion of the entire organ, 

 whereby the volume is increased, and the form of the anther, which 

 was developed in its regular manner as a leaf from the axis, is 

 perfected, but not changed. The outer layer of cellular tissue 

 originally clothed with a layer of epithelium, developes this into 

 a structure intermediate between epithelium and epidermis, not 

 unfrequently provided with stomates. The connective sometimes 

 exhibits hairs, the theca3 seldom. Sometimes the epidermal layer 

 is thickened at its outer edge by the presence of a layer of cells 

 elongated perpendicularly to the surface, so that it forms a pro- 

 jecting border (as in Gladiolus, Cassia, Passiflora, &c.) Perhaps, 

 with the sole (?) exception of plants flowering under water, one or 

 more layers of spiral fibrous cells exist in all anthers, but in 

 various modes of arrangement. Usually only one or two layers of 



