II. REPRODUCTIVE ADAPTATIONS. 



CHAPTER XXVI. 



PROTECTION AND DISTRIBUTION OF SPORES 

 AND SEEDS. 



The present knowledge of rejjroductive adaptations among 

 the fiowerless plants is very imijcrfect, though probably many 

 e.xist. This chapter must, therefore, discuss chiefly the 

 adaptations in the more complicated reproductive structures 

 of seed plants which have been most studied, with only 

 incidental allusions to such arrangements in the lower plants. 



I. Protection against bad weather. 



477. By movements. — Spores unfitted to resist low tem- 

 j)eratures or wetting nuist be jirotected from rain, cold, and 

 similar conditions, ^\'hen nectar is secreted in the llower 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 bentl their lea\'es so as to 

 close the flower (fig. 396), or arch the stalk so as to turn the 

 blossom into such a position that the rain or snow ^\■ill not 

 reach the sporangia or the nectaries. These mo\ements of 

 the leaves and stalk are combined in various wa)s to meet 

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



352 



