64 THE ANDROECIUM 



is to be distinguished from the form which is horizontal by versatility 

 (Fig. 129), by the presence in the latter of the two cells side by side, 

 in the former, end to end. 



Extrorse and Introrse Attachments. — Rarely the adnate form will 

 possess the connective upon the inner side (next the pistil), when it is 

 Extrorse by Attachment, in the normal form being Introrse. 



Forms of the Filament. — Besides these variations in the relation of 

 filament and anther, each is in itself subject to certain modifications, 

 some of which will be discussed in connection with appendages and 

 exaggerated growth. The general form of the filament is subject to 

 much variation which, being characteristic in a given species or genus, 

 requires specification. When cylindrical, either of uniform thickness 

 throughout or regularly tapering, it is Terete. When considerably 

 thickened toward and at the summit, so as to be club-shaped, it is 

 called Clavate. When flattened it is Complanate. Laterally Com- 

 planate is so flattened that the edges point toward and from the gynae- 

 cium, the broad sides to right and left. Dorsally complanate has the 

 edges pointing to right and left, the broad sides facing toward and from 

 the gynaecium. A dorsally complanate filament may have a sharp 

 ridge or keel running along its back, when it is called Carinate or Keeled. 

 If the ridge is less sharp and prominent it is Costate or Ribbed. It 

 may, upon the other hand, bear a groove, when it is called Channelled. 

 Rarely a filament is Triangulate in cross-section, or otherwise prismatic. 

 When tapering from a broad base to a rather acute apex, and rather 

 short, it is Subulate or awl-shaped. When very slender or thread- 

 shaped, it is filiform. When even more slender so as to be hair-like, 

 it is Capillary. 



Forms of the Anther. — The principal forms of anther are oblong, oval, 

 globular, reniform, quadrangular, or linear, and the base or apex may 

 be truncate, rounded, obtuse, acute, or pointed. An anther is occa- 

 sionally doubled upon itself, when it is styled Sinuous (Fig. 139). It 

 may even take the form of a horizontal ring (Fig. 134). This condition 

 is sometimes preceded by the loss of one theca. In any case of curva- 

 ture, even slight, of the anther, the same is characteristic and of value 

 in classification, as exemplified in the vast genus Solatium, where 

 attention to this character is well nigh indispensable. The filament is 

 also sometimes variously curved or reduphcate, and this condition may 

 be permanent or only temporary during the early stage of the flower, 

 as in Ardostaphylos (Fig. 145), where the powerful elasticity of the 

 filament assists in expanding the corolla. 



