THE BULIJ ]J()()K 



of the same race or nationality. When, however, two quite distinct 

 species or quite distinct varieties are fertilised with each other's 

 pollen (the operation may often be carried out both ways, so that 

 a "reverse" cross is produced) the plants are said to be hybridised, 

 and if any progeny result they are said to be " hybrids." Hybridis- 

 ing is analogous to marriage between quite distinct races. 



FORCING AND RETARDING BULBOUS 

 PLANTS 



For many years gardeners have been well acquainted with the 

 effects of a high or a low temperature upon plant life, and advantage 

 has been taken of this knowledge to bring some plants into flower 

 before their natural period, or to prevent them from flowering until 

 that period is over. The process by which plants are brought into 

 early flower is known as " forcing," while that by which they are kept 

 in check or suspended animation is known as " retarding." One pro- 

 cess is really the antithesis of the other. Thus in the winter months 

 when it is desired to have Tulips, Daffodils, Hyacinths, Crocuses, 

 Gladiolus, Liliums, etc., in flower, the plants are placed in a high 

 temperature and in an atmosphere more or less charged with 

 moisture. Before this stage is reached, however, the bulbs have 

 been placed in pots or boxes of soil with the tops just showing in 

 some cases, or the bulbs are only placed on the soil side by side in 

 others. Hardy kinds are then stood outside in a sheltered spot and 

 covered with about 6 inches of soil, ashes, or fibre, and left for a few 

 or several weeks. This protects them from frost, and root action and 

 top growth soon become established beneath the surface. This work is 

 generally done during October and November, so that the bulbs shall 

 be in different stages of development. When required for forcing 

 those first placed in pots or boxes are brought into the hothouses 

 first, as they will be most advanced in growth. For a few days but 

 very little light is allowed on them, but the temperature may be as 

 high as 70" to 80° F., and there will be also abundant moisture in the 

 atmosphere. At the end of a few days the yellowish tint of the 

 leaves or shoots begins to deepen into green. Then more light may 

 be given, and the flower-stems having been drawn up by the absence 

 of light now begin to swell the buds rapidly. Li due course (accord- 

 ing to the kind of plant that is being forced) the flowers begin to 



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