366 



LUSSOSS WITS PLANTS- 



frequent occurrence in potato bins in which there are tubers a year 

 or so old. The tuber endeavors to grow, but finding neither light 

 nor soil, it makes new tubers out of its own substance. 



Pig. 385. 



Section of a hill of potatoes growing in clay soil, drawn from life. 

 The old or " seed" tuber is at A. 



Suggestions. — Let the pupil answer some or all of the follow- 

 ing questions concerning a hill of potatoes. The queries may all 

 be answered easily by appealing to the growing plants, and some 

 of them may be answered from potatoes in the bin. How early 

 in the life of the plant do the tubers begin to form? Do the 

 tubers grow above the roots or below them? Does the position 

 vary between hard and mellow soils? Are potatoes produced on 

 rhizomes or roots? Do they form on the very end of the under- 

 ground stalk? Does one stalk ever bear more than one tuber, — do 

 tubers form sucoeBsively on a stalk, or does a stalk ever branch? 



