234 



THE NURSERY-BOOK. 



Knaurs (see page 56) are sometimes used. The olive can be 

 budded or grafted in a variety of ways. Twig-budding and 

 plate or flute-budding give admirable results. Twig-budding 

 is the insertion of a small growing twig which is cut from the 

 branch in just the manner in which shield-buds are cut. 



Omphalodes, Picotia. Boraginece. 



Freely increased by means of seeds planted in spring, 

 or by divisions. 



Oncidium. Orchidece. 



Division. In some species detachable buds are produced 

 in the inflorescence, and these give young plants. (See also 

 under Orchids.) 



Oncosperma, Keppleria. Palmce. 



Propagated by seeds or by suckers. 



Onion (A Ilium Cepa). Liliacece. 



Onions are mostly grown from seeds, which must be sown 

 as early as possible in spring ; or in the south they may be 

 sown in the fall. They are also grown from "tops," which 

 are bulblets borne in the flower cluster These are planted 

 in the spring, or in the fall in mild climates, and they soon 

 grow into large bulbs. "Sets "are also used. These are 

 very small onions, and when planted they simply complete 

 their growth into large bulbs. Sets are procured by sowing 

 seeds very thickly in poor soil. The bulbs soon crowd each 

 other, and growth is checked, causing them to ripen prema- 

 turely. Good sets should not be more than a-half inch in 

 diameter. Very small onions which are selected from the 

 general crop called "rare-ripes" are sometimes used as 



' sets, but they are usually too large to give good results. 

 Some onions the "multiplier "or "potato onions" increase 

 themselves by division of the bulb. The small bulb, which 

 is planted in the spring, splits up into several distinct por- 

 tions, each one of which will multiply itself in the same 

 manner when planted the following year, 



Onobrychis (Saintfoin). Leguminosce. 



Seeds, sown in spring where the plants are to remain. 

 Onosina (Golden Drop). Boraginece. 



Seeds, sown in the open in spring. Perennial species by 

 cuttings in summer. 

 Opuntia (Prickly Pear, Indian Fig). Cac'tece. 



Seeds grow readily, sown as soon as ripe in ordinary sandy 

 soil, either in the house or out-doors. The joints grow read- 



