414 LESSOJ!fS WITH PLANTS 



in Marsh's " The Earth as Modified by Human Action. " Teachers 

 who desire to acquaint themselves with the scientific methods of 

 working out the details of plant societies, should consult MacMil- 

 lan's "Observations on the Distribution of Plants Along Shore at 

 Lake of the Woods," in Minnesota Botanical Studies, Bulletin 9, 

 Parts X. and xi. 



Pupils often hesitate to collect plants for fear of being poisoned, 

 but there are only two plants, at least in the Northern States, which 

 are poisonous to the touch. These are the poison ivy (Fig. 84), 

 which climbs on fences, stumps and trees by means of roots, and 

 the poison sumac or poison oak (Fig. 85), a low bush inhabiting 

 swales. The Virginia creeper (Fig. 79) is often confounded with 

 the poison ivy, but it has five, and sometimes more, leaflets 

 whereas the ivy has but three. The Virginia creeper is harmless. 

 Of course, the pupil should never eat of wild fruits or roots with- 

 out knowing the plant. 



LXXXI. RECORDS OF THE SEASONS AND 

 THE YEARS 



525. The blooming of certain plants is asso- 

 ciated with the coming of spring. The dandelions, 

 the red maple, red-bnd, hepaticas, and their 

 train of woods flowers, the fruit-trees, the peeping 

 of the frogs and the return of the birds, all mark 

 the opening of a new season. No one goes to a 

 thermometer or barometer to see when spring has 

 come. In other words, plants and animals move 

 with the seasons, and afford, therefore, the best 

 records of the seasons. 



526. The keeping of the dates of blooming, 



