DEVELOPMENT OF PLANTS 459 



tion is an economical arrangement of tissues often to be seen. 

 It is noteworthy that these green fruits are often protected by 

 bitter, acrid juices and poisonous properties that finally give place 

 to attractive flavors, odors and colors, variations that are of 

 considerable assistance to seed protection and distribution. 



Fig. 319. Fruit of the maple: A, mature fruit of red maple {Acer rubrum). 

 B, schizocarp of Norway maple. The fruit split in half is still attached to 

 the receptacle by delicate stalks. 



Many of the members of this order contain acid or poisonous 

 juices, as in the scarlet fruit of the sumac, which were a source 

 of acetic acid to the early settlers of this country, or poisonous 

 oils, as in the poison ivy or poison oak {Rhus radicans) and' the 

 poison sumac (i?. Vernix). The former species is a climbing 

 vine or sometimes a shrubby plant with leaves divided into three 

 leaflets and with nut-like fruits (Fig. 320, B), while the poison 

 sumac is an erect coarse shrub ten to fifteen feet high, with large 

 pinnate leaves with reddish petioles and fruit clusters, as in the 

 poison ivy (Fig. 320, A). Both of these plants contain volatile 

 oils that cause the poisoning. The oil may readily be removed 

 by washing in water containing baking soda, which saponifies the . 

 oil, or in alcohol which dissolves it. With alcohol the washing 

 must be thorough in order not to spread the infection. Applica- 

 tions of alcohol containing sugar of lead (50 or 70 per cent, 

 alcohol) are also recommended, which treatment is followed by 



