II. REPRODUCTIVE ADAPTATIONS. 



CHAPTER XXVI. 



PROTECTION AND DISTRIBUTION OF SPORES 

 AND SEEDS. 



The present knowledge of reproductive adaptations among 

 the flowerless plants is very imperfect, though probably many 

 exist. This chapter, therefore, must discuss chiefly the 

 adaptations in the more complicated reproductive structures 

 of seed-plants which have been most studied, with only inci- 

 dental allusions to such arrangements in the lower plants. 



I. Protection against bad weather. 



383. By movements. — Pollen unfitted to resist low tem- 

 peratures or wetting must be protected from rain, cold, and 

 similar conditions. When nectar is secreted in the flower as 

 an attraction to insects it is liable to be washed out by rain 

 unless access of water to the interior of the flower is pre- 

 vented. To avoid these dangers, many plants upon the 

 approach of unfavorable weather bend their leaves so as to 

 close the flower (fig. 233), or arch the stalk so as to turn the 

 blossom into such a position that the rain or snow will not 

 reach the sporangia or the nectaries. These movements of 

 the leaves and stalk are combined in various ways to meet 

 the needs of each particular form. All of them are growth 



270 



