286 



EuG. Warming. 



quickly ensuing homogamy and self-pollination (Fig. 26a, ô^). 

 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. 26a. Cerastium alpinum. 

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

 5. — A, a^, a-: ^ in which four cal.-st. and one cor.-st. are abortive 

 (a'^). B: ^, scarcely expanded, but the stigmas [b^) are covered with 

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

 (fci) are still closed. C, Style of g with pollen which has germinated; 

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

 at this stage. — $. D, Style, "/1 and not =Vi (from beyond 73° N. lat.; 

 C.Ryder), and d^, d^, d^ stamens in various stages of reduction; d^ 

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



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

 minating pollen although seven anthers are still closed. This 



