^ HORTICULTURAL SOCIETY OF NEW YORK. 



The essential point which Mendel discovered in peas, and others are now 

 discovering in various fields of inquiry, is that, though a plant or an animal 

 may be made up of a great complex of characters, height, size, color, hairiness, 

 form of fruits and organs, etc., yet in a very considerable number of cases, a 

 number which increases almost every month, those characters may possess an 

 individuality manifested in the formation of the germ cells. When two varie- 

 ties differing in, say, color, or form, or hairiness, or whatever it may be, are 

 crossed together a "hybrid" is formed. That hybrid when it comes to make 

 its own germ cells, male cells, or female cells, makes them in a number 

 of cases, indeed in all Mendelian cases, such that each germ cell represents 

 one of the pure grandparental characters, and not both. That is the essential 

 discover}' of Mendel.. The cases that are most familiar are those in peas, the 

 subject on which he originally worked. If a pea with green cotyledons be 

 crossed with one having yellow cotyledons a hybrid is produced. That hybrid 

 grows up and bears peas in its turn. Those peas will be composed, each indi- 

 vidual pea, of a union of two germs, each germ being a carrier of either one or 

 ihe other of the pure parental characters. Therefore we may have two green 

 germs uniting, or two yellow germs uniting, or a yellow germ uniting with a 

 green. Each gamete in such a case is pure to one or the other of the two 

 parental characters which you first put into the hybrid. In other words, we 

 can recognize many dififerent characters in animals or plants which are unit 

 cliaracters, and in the formation of gametes are treated as distinct entities 

 or units. 



If, instead of using pure parental forms differing from each other in respect 

 of one pair of antagonistic — allelomorphic characters, as we call them — we use 

 parental forms distinguished in respect of two, three or more pairs of allelo- 

 morphs, then each germ cell in Mendelian cases will contain or transmit one 

 character only of each pair. 



To use an illustration : In chemistry you may have a body, say, a simple 

 salt, from which you can take out the base, or the acid radical, replacing the 

 base by another base, or the acid radical by another acid radical. You can in 

 that way decompose your substance into component parts, reforming them in 

 various combinations. So we must imagine a plant which has one element of 

 color, for example, another element of texture, etc., and we must conceive 

 that when two varieties are crossed together the unit characters can be com- 

 bined and recombined in the gametes of the hybrid, alternating with and 

 replacing each other by substitution. You can take out greenness and put in 

 yellowness; you can take out hairiness and put in smoothness; you can take 

 out tallness and put in dwarfness, etc. The characters have their fixed possi- 

 bilities of union, and hence it may be possible for us to form some mental 

 picture of the constitution of the organism. 



Now when we come to the question of the significance of these things to 

 the breeder or to the hybridist, it will be found that" the significance is exceed- 

 ingly great. I am afraid of saying that we have already reached a point when 

 the practical man who is doing these things with a definite, economic object or 

 commercial object in view can take the facts and use them for his definite 

 advantage. But we do for the first time get a clear sight of some of the 

 fundamentals on which he will in future work, and it cannot be now very 



