416 



The Journal of Heredity 



examples might be cited. Anyhow, the 

 genus is of secondary importance in 

 genetics. 



Species. — A substantive whose defini- 

 tion is much disputed. It may be 

 compared with that of a genvis. If genus 

 is a word which serves to group a number 

 of species, species is a word which unites 

 the varieties, races and variations of the 

 same type." Today we distinguish 

 systematic species and elementary 

 species. The first (also known as 

 Linnaean species or type species) are 

 described in most of the classical Floras 

 and works of botany. The second, 

 which are subdivisions of the first, are 

 also called Jourdan's species, elementary 

 species, etc. To make a long matter 

 short, let us say that they are races 

 which rc])roducc true from seeds. 



H}-brids. — Products of crossing two 

 systematic species. 



Crosses. — Products of crossing two 

 races or varieties of the same systematic 

 species, or of crossing descendants of 

 hybrids. 



Atavism (or Reversion). — A return of 

 crosses or hybrids to the characters of 

 their ancestors. 



Segregation and Selection. — These are 

 two nouns employed by genetists which 

 generally pass for synonyms. Never- 

 theless they have different meanings 

 which should be known by everyone 

 who takes an interest in seeking new 

 races of jjlants. 



NATURAL SELECTION. 



Segregation is a French word used as 

 early as the sixteenth century to repre- 

 sent the action Vjy which one sets apart 

 or separates from the whole, from a 

 mass, one or several objects which are 

 different from it. Selection is a word 

 first employed Vn' English breeders to 

 signify the choice for breeding of 

 animals endowed with the characters 

 which the breeder desires to fix in a 

 distinct variety of animals. Taken in 

 this sense, selection has the meaning of 

 marriage, if I dare to use the word, 

 between well-matched individuals. 

 Selection passed from English into the 



French language where it became 

 ]3opularized through the phrase natural 

 selection, invented by Charles Darwin. 

 According to the famous English scien- 

 tist, natural selection refers to the 

 predominance which nature yields to 

 any given species or variety, because of 

 the greater adaptation of its character- 

 istics to those of the environment, as 

 regards nutrition, conservation, repro- 

 duction, etc. — an adaption which allows 

 it to persist and brings about the dis- 

 appearance of less-favorably endowed 

 species which are unable to compete 

 with it. 



In horticultural practice, selection 

 signifies the choice of particular sub- 

 jects noticed among seedlings: ex- 

 traordinarly large or small sjjecimens, 

 ]3articularly early or late individuals, 

 etc. As for trees, one can often practice 

 selection on a single tree or shrub, 

 selecting branches which are more 

 fertile, precocious, late vigorous, etc., 

 than others. 



Pedigree culture or genealogical cul- 

 ture. — In this mode of cultivation, one 

 must start with seeds furnished by a 

 single individual, and must follow its 

 descendants for a number of generations 

 to make sure that it is fixed. If it is 

 variable, the study of its variations 

 should be pursued until it is decided that 

 they are not going to furnish the 

 desired results. 



Other technical words used in plant 

 breeding will be explained as they are 

 employed in the course of this study. 

 As I have promised a number of persons 

 to discuss roses, I will now keep that 

 promise by giving some practical direc- 

 tions for rose breeding to amateurs. 



SELECTION OF BRANCHES. 



I note in La Petite Revue a report 

 of the exjiosition held at Antibcs, on the 

 French Riviera, last March, in which 

 M. J. Lefevre makes the follo\ving 

 comment which bears, in part at least, 

 of the selection of branches: 



" In a very different way, M. Dhumez 

 was able to get from Nature more than 

 she had ever wanted to give. Disrc- 



'Thc lay reader will probably be less confused if he retains the old definition, tlial a siiecies is 

 a group of or^anisTi-? which interbreed freely. ^Thc Editor. 



