190 THE TEACHING BOTANIST 



but it is especially for the observation of ecological and 

 physiological phenomena, and the use of experiment in their 

 interpretation. 



In observation, they should not fail of themselves to see 

 and record, in addition to the more obvious features, the axil- 

 lary buds of the cotyledons of the Beans, stipules on the 

 Lima Bean (united in pairs at the first leaves), the arrange- 

 ment of the earlier roots in four ranks (answering to their 

 origin from the four fibro-vascular bundles), and the fact that 

 leaf veins taper from base to tip, and are all united with one 

 another. The position of the terminal bud in the Horse 

 Bean should also be seen correctly. 



Exercise 20 is most important to compel clearness in mor- 

 phological ideas, as is particularly Exercise 21. 



In ecology they may be led to see that the failure of 

 cotyledons to come above ground in two of the seedlings is 

 due to their lack of usefulness as leaves on account of their 

 shape. In the Morning-glory, the small supply of nourishment 

 in the seed explains the late appearance of the plumule ; the 

 material to make it must first be formed in the green cotyle- 

 dons. Most students can recall the roots from joints above 

 ground in adult Corn plants. They should be encouraged 

 always to call to their aid any previous knowledge of this kind 

 which they may possess. 



Experiment No. 2. --In preparation for this the teacher 

 will do well to direct the students' attention beforehand to the 

 obvious cases of turning toward light in the boxes of seedlings, 

 and the cases known to all of them in house plants. Two 

 simple and similar plants in small pots should be taken 

 (Tropicolum, i.e. "Nasturtium," is very good). They should 

 be placed in strong one-sided light, but one of them should 

 be kept revolving in a horizontal plane on a clinostat. Of 



