ADJUSTMENT TO TEMPERATURE 



117 



flower, or of stamen-bearing flowers. A large production of 

 pollen is secured in many open flowers, such as the buttercup, 

 anemone, strawberry, cinqfoil, etc., by a large number of stamens, 

 and doubtless compensates for the great loss arising from the ease 

 with which many insects may reach the pollen and eat it. Among 

 wind-pollinated plants the greatest loss occurs in the dioecious 

 trees, such as the cottonwood and ash, and the monoecious conifers, 

 e.g., pines, spruces, and firs, in which the pistillate cones are 



Fig. 28. Extremes of pollen production. 1, an orchid, Orchis sp.; p, pol- 

 len mass in anther cell; r, retinaculum; s, stigma; 2, a baobab flower 

 (Adansonia) with a column of stamens. (1 after Le Maout and De- 

 caisne, 2 after Baillon.) 



usually above the staminate ones. The need of com])ensation 

 in such cases is very great, and the amount of pollen necessary is 

 enormous. Indeed, in many coniferous forests, nothing is found 

 so universally scattered as pollen grains that have miscarried. 

 In many trees the great loss of pollen is offset by the development 

 of a large number of flowers, especially of imperfect ones in which 

 the material ordinarily available for sepals, petals, and jnstils is 

 used for stamens. This is the case in polygamous flowers, such 

 as those of the maple. Not all wind-pollinated flowers jiroduce 

 a large amount of pollen. In the grasses and sedges, for example, 

 the number of stamens is usually 1-3. This is probably to be 

 explained by their habit. They are low-growing and usually 

 densely associated, in consequence of which the i)ollen is carried 

 through the whole group of individuals before it is blown away. 

 As would be expected, the number of stamens and hence the 



