24 



change color, or at least the lower leaves, when the water 

 dries up in early summer, as Polygonum, Ludwigia, and 

 Statice, which change to red or purple. 



Also in July a considerable number of leaves of Pyrus 

 arbutifolia, L. in similar dry soil were seen of a bright red 

 color ; it was found that nine-tenths of these had been 

 punctured or otherwise injured by small insects which had 

 sucked their juices. The latter part of July, Ampelopsis 

 qninquefolia, Michx. often displays more or less red leaves. 

 They are most commonly seen in sunny places, especially 

 on stone walls and dedges. Their color is also induced 

 partly l)y insects which prefer sunshine to shade, and in 

 part to excessive heat, direct and reflected, increasing trans- 

 piration in excess of absorption. The temperature in such 

 situations is frequently 15 to 20 degrees higher than in the 

 shade and often above 100 degrees Fahrenheit. A portion 

 of the same vine if shaded from the sun's rays is likely to 

 be green and not attacked by insects. 



July 20, many yellow leaves were seen on black walnut 

 (Juglans nigra), and butternut {J. cinerea). They were 

 caused by a caterpillar | in. long covered with a fluffy, 

 white, woolly substance which stood erect on their backs. 

 This was doubtless for protection from enemies, as it finally 

 disappeared. They bit a small crescent shaped hole about 

 an inch from the base of the leaf, severing the midrib at 

 that point and apparently sucked the juices Of the nu- 

 merous fallen leaves every one had the midrib punctured at 

 the same spot. 



About the m,iddle of August, bright crimson leaves were 

 seen on a scarlet oak ; this was two months before the leaves 

 of this oak change color usually. It was found that every 

 colored leaf had been punctured on the midrib precisely as 

 those of Juglans I 



Some leaves of potted Pelargoniums in February were 

 noticed to be red at the tips. The broad, heart shaped 

 leaves, of a succulent character, were found to have been 



