CHAP. I. HOMOSTYLED PRIMULAS. 49 



a special adaptation for counteracting their greater 

 liability to receive their own pollen, and thus for 

 checking self-fertilisation. But from facts with respect 

 to other species hereafter to be given, this view can 

 hardly be admitted. In accordance with the above 

 liability, when some of the species of Primula were 

 allowed to fertilise themselves spontaneously under 

 a net, all insects being excluded, except such minute 

 ones as Thrips, the short-styled flowers, notwith- 

 standing their greater innate self-sterility, yielded 

 more seed than did the long-styled. None of the 

 species, however, when insects were excluded, made a 

 near approach to full fertility. But the long-styled 

 form of P. Sinensis gave, under these circumstances, 

 a considerable number of seeds, as the corolla in falling 

 off drags the anthers, which are seated low down in 

 the tube, over the stigma, and thus leaves plenty of 

 pollen on it. 



Homostyled species of Primula. It has now been 

 shown that nine of the species in this genus exist under 

 two forms, which differ not only in structure but in 

 function. Besides these Mr. Scott enumerates 27 other 

 species * which are heterostyled ; and to these probably 

 others will be hereafter added. Nevertheless, some 

 species are homostyled; that is, they exist only under 

 a single form; but much caution is necessary on this 

 head, as several species when cultivated are apt to 

 become equal-styled. Mr. Scott believes that P. 

 Scoiica, verticillata, a variety of Sibirica, elata, mollis, 

 and longiflora,\ are truly homostyled ; and to these many 



* H. Miiller has given in ' Na- f Koch was aware that this spe- 



ture,' Dec. 10, 1874, p. 110, a draw- cies was homostyled: see "Tre- 



ing of one of these species, viz. the viranus iiher Dichogamie nach 



Alpine P. rillosa, and shows that it Sprengel und Darwin," 'Bot. Zei- 



is fertilised exclusively by Lepi- tung,' Jan. 2, 1863, p. 4. 

 doptera. 



