32 DIMORPHOUS PLANTS. [chap. 



is longer. Thus Nigella, according to Sprengel, is 

 male for six days, after which the stigma comes to 

 maturity and lasts for three or four. (Das entdeckte 

 Geheimniss der Natur, p. 287.) 



Fig. 34 represents a flower of Myosotis versicolor (a 

 species often known as the Forget-me-not), when just 

 opened. It will be observed that the pistil projects 

 above the corolla and stamens, so that it must be first 

 touched by any insect alighting on the flower. 

 Gradually, however, the corolla elongates, carrying 

 up the stamens with it, until at length they come 

 opposite the stigma, as shown in Fig. 35. Thus, if 

 the flower has not already been fertilised by insects, it 

 is almost sure to fertilise itself. 



I now pass to the third of the principal modes by 

 which self-fertilisation is prevented. In the flowers 

 hitherto described, while the several species offer the 

 most diverse arrangements, we have met with no 

 differences within the limits of the same species, ex- 

 cepting those dependent upon sex. But there are 

 other species which possess flowers of two or more 

 kinds, sometimes, as in the violet, adapted to dif- 

 ferent conditions, but more frequently so constituted 

 as to ensure cross-fertilisation. In some of the violets 

 ( V. odorata, canina, &c.), besides the blue flowers with 

 which we are all so familiar, there are other, autumnal, 

 flowers almost without petals and stamens ; which 

 indeed have scarcely the appearance of true flower.«, 

 but in which numerous seeds are produced. " Cleis- 

 togamoiis" flowers, as these have been called, occur 

 also in Lamiuui amplexicaule (Figs. 36 and 37), Oxalis 

 acetosella, Trifolinm siibterraneum, and other plants 



