398 THE NURSERY-MANUAL 



Platanus (Plane-Tree. Buttonwood. Sycamore, improperly). 



Platanacece. 



Usually propagated by seeds, sown in spring, slightly covered with 

 earth and kept moist and shaded, but layers, ripe-wood cuttings 

 and greenwood cuttings under glass in June taken with a heel may 

 be employed. Varieties may be grafted in spring on seedlings 

 of one of the species. 



Platycerium (Stag's-HornFern). Polypodiacece. 



Propagation chiefly by division ; sometimes by spores. See Ferns. 



Platyclinis. Orchidaceoe. 



Propagated by side-growths from the old pseudobulbs. When 

 no natural break occurs, the plants may often be induced to break 

 by slightly twisting, or notching the rhizome with a sharp knife. 

 See Orchids, page 372. 



Platycodon, Wahlenbergia. Campanulacece. 



Propagated by seeds, and old plants by division in spring if care 

 is taken with the fleshy rootstock. 



Pleione. Orchidaccoe. 



Propagation as for ccelogyne. See Orchids, page 372. 



Plum (Prunus, many species) . Rosacece. 



So many species of plums are in cultivation, and the varieties of 

 the same species are often so different in constitution and habit, that 

 it is difficult to give advice concerning their propagation. All the 

 species grow readily from fresh well-ripened seeds. The pits or 

 stones should be removed from the pulp and then stratified until 

 spring. If they are allowed to freeze, the germination will be more 

 uniform, as the pits will be more easily opened by the swelling 

 embryo. Plum pits are rarely cracked by hand. The strong-growing 

 species and varieties, especially southwards, will give stocks strong 

 enough to bud the first season ; but the weaker ones must stand 

 until the next season after the seeds are planted. In all the north- 

 ern states, however, plum pits are usually sown in seed-beds, in the 

 same way as apple and pear seeds. The seedlings are taken up in 

 the fall, and the following spring set out in nursery rows, where they 

 are budded in August. 



Plums are extensively grown from suckers, which spring in great 

 numbers from the roots of many species. In France this method of 

 propagation is largely used. So long as graftage does not intervene, 



