THE LEAF 



96. Winged petiole of 

 Polymnia. 



97. Water cups of Silphiur 

 perfoliatum. 



instance, do housewives sometimes set the feet of their 

 cupboards in vessels of water ? 



60. Protection against Excessive Light and Heat. With 

 plants growing in very hot, dry climates, or in exposed 

 situations, it is often necessary to guard against too rapid 

 transpiration by shutting off the 

 direct rays of the sun from the sto- 

 mata, just as we close our blinds in 

 summer to keep the heat out. The 

 common blackberry lily {Be lam 

 canda) of our old red hillsides, and 

 98. Cross sections of the others of the iris family, to which 



c. roiled up to prevent too vertically so as to expose only the 



rapid transpiration. dps ^ Q ^ full ^^ Qf ^ nOQnday 



sun. Many swamp herbs like the sweet flag (Acorns 

 calamus], the cat-tails, and yellow-eyed grass (Xyris) have 

 the same habit, the pools and marshes in which they grow 

 often becoming dry in summer ; and moreover, even though 

 there may be plenty of moisture, they are very dependent 

 upon it and need to retain a good store. Strongly revo- 

 lute margins, such as are found in many sand plants 

 growing along the seashore, produce the same effect by 

 inclosing the stomata in the hollow trough or cylinder 

 formed by their recurved edges. 



