The Science of Plant Growing 67 



resulting seedlings named, Laeliocattleya or Catlselia, by compounding the 

 names. Three genera have been united by crossing the product of the 

 first two with a third, namely, Brassavola, Cattleya, and Laelia, and indi- 

 cated by the name Brassocatlselia. 



Hybrids are by no means always sterile, as was at one time supposed, 

 when they were termed "mules". The hybrid progeny of Orchids, Be- 

 gonias, Roses, and other plants may be used as parents for still further 

 improving the race. To what extent hybridization can be carried is un- 

 certain, as it largely depends on sexual affinity. Some varieties refuse 

 to cross, and many species refuse to hybridize with one another. The 

 difficulties are increased when it is attempted to mate species belonging 

 to different genera, and the members of different natural orders refuse to 

 hybridize at all. When species are distantly related, the possibilities of 

 hybridizing them can only be determined by experiment. When this is 

 done artificially it largely depends on the skill of the operator, who must 

 get the pollen in mature and good condition, and apply it to the stigma 

 when perfectly developed and receptive, either moist, as in an Orchid or 

 Rose, or covered with a fine downy pile, as in a Carnation, Begonia, Chrys- 

 anthemum, or Cineraria. To make sure of the pollen applied being effective, 

 the anthers of the flower to be operated upon must be removed before they 

 have burst, and after applying the pollen the flower should be covered with 

 thin gauze to exclude insects for a few days till the pollen has time to take 

 effect. In winter and under glass this is scarcely necessary, and in summer 

 tiffany may be put over the open ventilators to exclude insects. 



Plants grown for seed in the open field must be kept widely apart, if 

 they are at all closely related, or insects may mix the stocks by carrying 

 the pollen of one to another. Varieties of the cabbage tribe, such as 

 Cauliflower, Kale, Brussels Sprouts, and Cabbages are very liable to be 

 indiscriminately crossed in this way and rendered useless. Sports may be 

 explained by the characters of a cross-bred or hybrid plant becoming 

 separated or dissociated in certain of the buds on the stem, and the flowers 

 of such buds, or the shoots from them, are of a different colour. 



Various Forms of Fruit. As the result of the fertilization of the 

 egg cell and the production of an embryo, the pistil becomes the young 

 fruit. Usually this includes only the ovary and stigma, with the style if 

 present, as well as the ovules. In those cases where the receptacle grows 

 up around and adheres to the ovary walls, that also forms part of the fruit, 

 as in the Cucumber, Melon, Apple, and Daffodil, with the withered remains 

 of the flower on the top of it. The simplest forms of fruit may be seen 

 in the Buttercup and Strawberry, in which the small, mature fruits 

 resemble seeds. In the Christmas Rose and Columbine it becomes dry, 

 splits along one edge, and is termed a follicle; in the Pea it splits along 

 both edges and is named a legume or pod. The Pansy, Poppy, and Snap- 

 dragon have dry seed vessels, opening by valves or pores and named 

 capsules. The fruit of the Gooseberry and Currant is a true berry, because 

 inferior, one-celled, and pulpy. The fruit of the Apple is called a pome. 



