PROPAGATION BY TRUE ROOTS 



37 



Tubers are used for propagation of all plants which yield them. 

 The most common examples of tuber-forming plants are the Irish 

 potato and the Jerusalem artichoke. 



A tuber is a fleshy portion of the underground stem, bearing 

 ''eyes' ' or true buds arranged in somewhat regular spirals. 



The Potato. — An examination of several Irish potatoes will 

 reveal the fact that the two ends are not alike. The stem end is 

 where it was attached to the parent plant. The opposite end is 

 called the "eye' ' end because the eyes or true buds are more abun- 

 dant at that end. These eyes 

 usually start growth first. If 

 the first growth is killed by 

 frost the others may grow 

 later. If long pieces are cut for 

 planting they may bear both 

 types of eyes. The stem end of 

 large potatoes might almost 

 as well be saved for table use 

 because of so much food and 

 sc few eyes. Do not plant 

 very small pieces with 

 only one or two eyes unless 

 potatoes are very expensive. 



Seed potatoes should be spread on a floor in a rather light place, 

 but not in direct sunlight. If they remain here for several days 

 they will become greenish in color and the sprouts will be strong 

 and the subsequent growth will be inore vigorous. (Fig. 83.) 



Propagation by True Roots. — Very few plants can be propa- 

 gated by true roots alone. Plants of the blackberry group are very 

 notable examples. Methods used in propagating blackberries are 

 described under cuttings, in the next chapter. 



The peony and some other fleshy-rooted herbaceous plants, 

 including the sweet potato, will grow somewhat readily from the 

 fleshy roots. 



The apple, pear, quince, and some plums are quite commonly 

 propagated by means of root grafts. But in this type of propaga- 

 tion the new twig with its buds is grafted on the root or piece of 

 root. A rather complete union is formed before the new plant 

 begins growth. Root grafting is fully described in Chapter VI. 



Fig. 24. — Section of hyacinth bulb showing 

 bulblets forming at each scale. These are later 

 set out and developed to full size. 



