148 

 mother come together in the cell, and in the cell only; and 

 all characters, whether relating to a large part of the organ- 

 ism, or merely to a single cell, can only be determined by 

 processes taking place within the substance of one or of 

 many cells " 



Kerner says: "Some of their attributes and external char- 

 acters are derived from the paternal, some from the maternal 

 stock. If the relative admixture of the two stocks were to be 

 determined in the case of the hybrid by summing up the 

 characteristics transmitted from each source, the share of 

 each parent would, in many cases be found to be half. In 

 such a case it is usual to say that the hybrid is a mean be- 

 tween its parents. Examples are afforded by Geum hybridum, 

 which originates from crossing Geum montanum and G. 

 rivals."' 



Hybrids are changed with reference to the production of 

 seed, so much so that hybrids seldom if ever produce seed, 

 and therefore do not propogate sexually. They show a 

 marked change with reference to variability. In closely 

 related species they flower earlier and longer with usually a 

 luxuriant growth. 



Focke states that he is of the opinion that genera with 

 zygomorphic flowers, belonging to orders with actinomorphic 

 flowers, show especial prediliction for hybridization. Pelar- 

 gonium of Geraniaceae and Nicotiana of Solanaceae. It appears 

 to be difficult to hybridize plants growing in different 

 situations. 



• "As a general thing, when species are closely related 

 hybrids are more easily produced, as in many Solanaceae, 

 Caryophyllaceae, Iridaceae Salicaceae. In other orders it is 

 difficult to obtain hybrids, as in Coniferae and Leguminosae. 

 Species of Vitis, Salix and Dianthus hybridize readilj', but 



