NATURE OF PLANTS 39 



offers little support. If now the water in the intercellular spaces 

 of the separating layer should freeze, the expansion of the water 

 as it freezes would so rupture the remaining tissue that we would 

 have the familiar sight of the leaves falling in a shower in the 

 morning after a frost — either of their own weight or with the 

 slightest breeze. It will also be noticed that owing to the for- 

 mation of the cork layer or the drying up of the delicate cells of 

 the separating layer, the scar formed by the fall of the leaf is 

 nicely healed and closed against any loss of fluids or the entrance 

 of any organism (Fig. 28, C). 



The casting off of the leaves reduces the area of the plant 

 that is exposed to the unfavorable conditions to a minimum. 

 This reduction of the surface is effected in one way or another 

 by a great variety of plants. Much of our spring vegetation 

 is possible by reason of it. The spring beauties, anemones, fawn 

 lilies, jack-in-the-pulpits, etc., practically complete their growth 

 before the larger summer forms appear. During this short period 

 sufficient food is manufactured by the leaves to mature the seeds 

 and fill the storage organs in the underground bulbs and stems. 

 When the larger forms appear later in the season these plants 

 are overshadowed, their leaves wither, and they are reduced to 

 the small bulbs and stems hidden in the earth. In this condition 

 they remain until the next spring when the abundance of stored 

 food enables them to complete their growth before other com- 

 peting forms appear. 



This ability to reduce the surface of the plant body makes 

 possible the existence of much of the plant life of arid and desert 

 regions. During the short rainy seasons the stored foods enable 

 the plant to quickly put forth the leaves which in turn manu- 

 facture the foods which are stored in seeds, stem and roots. 

 Then practically all trace of these plants is destroyed by the 

 drought. Only the seeds or a greatly reduced portion of the 

 plant remain alive and this is often further protected by being 

 hidden in the ground. A return of favorable conditions quickly 

 awakens these plants to growth. Mr. Dan Beard relates an 

 interesting experience in the desert regions of Texas that illus- 

 trates this feature of plant life. At the close of the dry season 



