57 



Handbook of Nature-Study 



PRICKLY LETTUCE, A COMPASS PLANT 

 Teacher's Story 



The more we know of plants, the more we admire their ways of attain- 

 ing success in a world where it is only attained by a species after a long 

 struggle. While plants may not be conscious of their own efforts for 

 living on successfully, they have developed them just the same, and they 

 merit our admiration perhaps even more, than as if their strategy was the 



result of conscious thought. 

 The prickly lettuce has a 

 story to tell us about suc- 

 cess attained by the pre- 

 vention of exhaustion from 

 thirst. In fact, the success 

 of this weed depends much 

 upon its being able to live 

 in dry situations and with- 

 stand the long droughts of 

 Hate summer. The pale 

 green stems grow up slim 

 and tall, bearing leaves 

 arranged alternately and 

 from all sides, since be- 

 tween two, one of which is 

 exactly above the other, 

 two other leaves are borne. 

 Thus, if the leaves stood out 

 naturally, the shape of the 

 whole plant would be a 

 somewhat blunt pyramid. 

 But during the hot, dry 

 weather, the leaves do not 

 stand out straight from the 

 stem; instead, they twist 

 about so that they are 

 practically all in one plane, 

 and usually point north 

 and south, although this is 

 not invariably the case. 



The way this twisting is accomplished is what interests us in this plant. 

 The long spatulate leaf has a thick, fleshy midrib, and at the base are 

 developed two pointed lobes which clasp the stalk. The leaf is soft and 

 leathery and always seems succulent, because it retains its moisture; it 

 has a ruffled edge near its base, which gives it room for turning without 

 tearing its margin. Each leaf tips over sidewise toward the stem, and as 

 far as necessary to bring one edge uppermost. Thus the sun cannot 

 reach its upper surface to pump water from its tissues. The ruffled 

 margin of the upper edge is pulled out straight when the leaf stands 

 in this position, while the lower margin is more ruffled than ever. Thus, 

 it stands triumphantly, turning edgewise to the sun, retaining its moisture 

 and thriving when cultivated plants are dry and dying. 



A common compass plant. 

 Photo by Cyrus Crosby. 



