360 



PLANT STUDIES 



that of Gymnosperms, and has lost any semblance to a leaf. 

 It consists of a stalk-like portion, the filament^ and a 

 sporangia-bearing portion, the anther (Figs. 319, 321, A). 



Fig. 320. Cross-section of anther of thorn apple (Datura), showing the four imbedded 

 sporangia (a, p) containing microspores; the pair on each side will merge and 

 dehisce along the depression between them for the discharge of pollen. — After 

 Frank. 



The filament may be long or short, slender or broad, or 

 variously modified, or even wanting. The anther is simply 

 the region of the sporophyll which bears sporangia, and is 



\v//i 



Fig. 321. Diagrammatic cross-sections of anthers: A, younger stage, showing the 

 four imbedded sporangia, the contents of two removed, but the other two con- 

 taining pollen mother cells {pm) surrounded by the tapetum (t)\ B, an older stage, 

 in which the microspores (pollen grains) are mature, and the pair of sporangia on 

 each side are merging together to form a single pollen-sac with longitudinal 

 dehiscence.— After Baillon and Luerssen. 



therefore a composite of sporophyll and sporangia and is 

 often of uncertain limitation. Such a term is convenient, 

 but is not exact or scientific. 



