218 THE STRUCTURE OF FLOWERS. 



apparently trnlj heterostyled, but from Mr. Darwin's obser- 

 vations be tbinks tbe sbort-stvled incapable of fertilisation ; 

 moreover the anthers of tbe long-styled form were " browm, 

 tougb, and devoid of pollen." He considers that, from baving 

 been beterostyled, it has now become dioecious, or else gyno- 

 dioecious. 



M. W. Durek has sbown * tbat several genera of 

 Buhiacece are beterostyled in form but quite dioecious. 



Faramea affords anotber curious difference. In tbe long- 

 styled form tbe stigma is sbort and broad ; in tbe sbort- 

 styled, it is long, thin, and curled. Tbe anthers of tbe 

 sbort-styled are a little larger than tbose of tbe long-styled, 

 and tbe size of their pollen grains are as 100 : 67. But tbe most 

 remarkable difference (of wbicb no otber instance is known) 

 is in tbe fact tbat wbile tbe pollen grains of tbe sbort-styled 

 forms are covered witb sbarp points, tbe smaller ones are 

 quite smooth. Tbe anthers, moreover, rotate outwards in 

 the short-styled, but do not do so in tbe long-styled flowers. 

 A similar rotation takes place in some of tbe Cruciferce, and 

 facilitates intercrossing. A somewbat analogous torsion 

 occurs in some styles and stigmas, as of Linum jperenne, 

 Luzula arvensis, Begonia, etc. 



Tbe smaller and smootb pollen, in tbe more degenerate 

 condition of tbe long-styled form, is suggestive of the origin 

 of tbat of wind-fertilised flowers, wbicb bas sometimes 

 acquired tbe same form. Indeed, tbe two forms of pollen 

 (figured by Mr. Darwin at p. 129 of Forms of Flowers) exactly 

 correspond to tbe very common spinescent form in inter- 

 crossing species of Comijositoey and to tbat of tbe anemopbilous 

 Artemisia of the same order, respectively. 



Tbe general conclusion, therefore, derived from tbe com- 



* Sur V Organisation Florale chez quelques Ruhiacees. Ann. Jard. 

 Bot. Biiitenzorg 3, p. 105. 



