286 



Eue Warming. 



quickly ensuing homogamy and self-pollination (Fig. 26a, b 1 ). 

 The relative length and position of the stamens and pistil 

 is shown in the figures. Before the cor.-anth. are opened 

 the styles may be covered with germinating pollen. I have 

 even seen homogamy set in immediately, even before the 

 flowers had expanded fully, and while the styles were still 



Fig. 2(3 a. C er ostium alpinum. 

 From West Greenland (about 64°— 70° N. lat.). 

 $. — A, a 1 , a 2 : £ in which four cal.-st. and one cor.-st. are abortive 

 (a 1 ). B: £, scarcely expanded, but the stigmas (b 2 ) are covered with 

 germinating pollen; three cal.-anth. have opened, but the cor.-anth. 

 (b 1 ) are still closed. C, Style of £ with pollen which has germinated; 

 all the anthers have opened and are empty, c 1 shows the longest papillæ 

 at this stage. — $. D, Style, "A and not 31 /, (from beyond 73° N. lat.; 

 C. Ryder), and d 1 , d 2 , d 3 stamens in various stages of reduction; d l 

 has fibrous cells in the wall, but no pollen. E, Seed. (E. W.) 



erect: in Fig. 1, B, b 1 , b 2 the stigma is covered with ger- 

 minating pollen although seven anthers are still closed. This 



