149 

 Si'ene with difficulty; Nicotiana, Verbascum and Oeum easily, 

 but Solnnnm, Linaria and Potentilla with difficulty. Some- 

 times hybridization will not occur in closely related species, 

 as the apple (Pyrus malus) and pear [P. communis). 



Kroelreuter observed in his hybrids that in part they 

 partook more of the mother than of the father, or the re- 

 verse. In some cases where one parent had yellow flowers 

 and the other red, the hybrid had variegated flowers. When 

 a hybrid was produced between an early fliowering and a 

 late-flowering plant, the hj'hrid was between the two in time 

 of flowering,. 



Hybrids of species of closer relationship, or the crosses 

 are usually strong and productive. Such plants are char- 

 acterized by their greater size, rapid growth, early matura- 

 tion of the flowers, longer life, greater productiveness and 

 unusual size of the separate organs. In hybrids produced 

 from Rhododendron arboreum and Catawbiense the flow- 

 ers mature earlier. In some species of Rhododendron and 

 many other plants hybrids are sterile. Hybrid seedlings of 

 Nymphoea alba are difficult to grow. 



Hybrids of Salix viminalis and S- purpurea are 

 said to be much more sensitive to frost than the species. On 

 the other hand crosses of Nicotiana suaveolens and N- 

 tabacum-lattissimum resist frost better than the species. 



Focke adds, "That hybrids of different species contain 

 less pollen in their anthers than those of the mother plant, 

 and the fruit contains a smaller number of seeds. Frequently 

 they contain neither pollen nor seed. " It is also a -well- 

 established fact that the closer the relationship between 

 species the easier it will be to obtain fertile hybrids. 



Sachs says: "The characteristics of the parent-forms 

 are as a rule so transmitted to the hybrid that the influence 



