176 ANGIOSPERMAEDICOTYLEDONES 



warm weather. Stellaria media, var. pallida, is indeed in some places completely 

 cleistogamous. Most species secrete nectar very abundantly. This usually trickles 

 down from the nectaries between the bases of the petals on to the spoon-shaped 

 sepals, which often project horizontally. The larger flowers of some species relatively 

 poor in nectar are visited much less than the smaller flowers of other species which 

 are more richly supplied. But the small flowers of some species which secrete 

 a comparatively large quantity of nectar e.g. those of Arenaria serpyllifolia and 

 Sagina Linnaei, var. macrocarpa remain almost unvisited. Probably this difference 

 as regards visits depends upon variations in the composition of the nectar : presum- 

 ably that of Arenaria serpyllifolia and similar species are deficient in certain odorous 

 substances, so that insects have difficulty in detecting it. 



The following species are known to be gynodioecious (gd.) or gynomonoe- 

 cious (gm.). 



Sagina nodosa Fenzl, gd. in Denmark (Warming) and Belgium (MacLeod); 



S. Linnaei Presl, gd. and gm. (Schulz) ; 



Spergula arvensis Z., gm., more rarely gd. (Schulz); 



S. vernalis Willd., and S. pentandra Z., gm. and gd. (Schulz) ; 



Spergularia media Presl, gd., rarely gm. (Schulz); 



S. salina Presl, ditto ; 



S. rubra Presl, gm. and gd., as also Alsine verna BartL, Cherleria sedoides Z., 

 Mochringia muscosa Z., Arenaria serpyllifolia Z., A. biflora Z., A. ciliata Z., Holo- 

 steum umbellatum Z., Stellaria nemorum Z., S. media Cyr., S. Holostea Z., S. uligi- 

 nosa Murr. (mostly according to Schulz); 



S. graminea Z., gm. (MacLeod) ; 



S. palustris Ehrh., gd. (Warming, Ludwig, Miiller); 



S. graminea Retz., gd. (Tullberg, Warming, Miiller, Ludwig, Schulz); 



Malachium aquaticum Fries, gd. (Ludwig) and gm. (Schulz); 



Cerastium arvense Z., gd. and gm. (Schulz); 



C. triviale Link, gd. (Ludwig), and gm. (Schulz) ; 



C. glomeratum Thuill., gd. (Ludwig); 



C. brachypetalum Desp., gm., moderately gd. (Schultz), so also for C. semi- 

 decandrum Z., C. pallens F. Schultz, C. obscurum Chaub., C. trigynum VilL, and 

 C. latifolium Z. ; 



C. alpinum Z., gd. (Ludwig). 



126. Sagina L. 



Small whitish, protandrous, homogamous or protogynous flowers, with half- 

 concealed nectar secreted at the bases of the stamens. 



436. S. procumbens L. (Schulz, Beitrage,' II, pp. 38-9.) There are four 

 small nectaries at the bases of the filaments. The white petals, usually four in 

 number, are smaller than the sepals, of which an equal number are present. The 

 four or five stamens develop simultaneously with the four or five stigmas. Automatic 

 self-pollination is inevitable, for the flowers remain closed in dull weather. In 

 Greenland, according to Warming, the anthers, even in the open flower, come into 

 contact with the short, greatly spreading styles. The same investigator observed 

 female flowers as well as hermaphrodite ones in Denmark. 



