99 
Some Recent Work on Hybrids in Plants . 
the aleurone-layer (whether long or short), the colour of the grain 
coat, and the colour of the endosperm and aleurone-layer in the first 
generation. Under the Hieracium type are included pairs of 
characters in relation to the form and size of the grain, the weight 
relation of the embryo and endosperm, the size of the plant and 
fruit spike, etc. 
These observations show clearly that in similar races, and even 
in one and the same race, characters of the three different categories 
may he found together. The matter is further complicated by the 
fact that schizogonous characters were sometimes found to be altered 
in value by the separation which takes place at gamete formation in 
the f rst generation (as is shown by the change of the characters 
for the colour of the endosperm and aleurone-layer from homody¬ 
namic to heterodynamic), and by the fact that the relative value 
of the two characters of a homodynamic pair is often affected 
(1) by the individuality of the gametes, (2) by the individuality of 
the plants, ( 3 ) by the nature of the race to which the plant belongs/' 5 
Before considering further recent work, it will be convenient to 
give a brief account of the various types of behaviour which may 
be observed in a pair of characters of a hybrid during vegetative 
development (Correns, 1901 , a, b). In the case of a homodynamic 
pair of characters the two characters may be equally strong 
in all cases, there will then be only one kind of hybrid which will be 
exactly intermediate in character between the two parent forms*. 
Using A, a, as before, to represent the parental characters, and H 
as representing the hybrid, the condition may be then represented 
thus:— 
.H. (1) 
A A 
The two characters may, however, be unequally strong, but with 
*he same one always the stronger and to the same degree, the 
hybrid will then approach in character one of the parents:— 
.H. ( 2 ) 
A A 
*Sex was found to have little real effect except iu relation to the 
characters of the hybrid endosperms to be discussed later. 
The form and size of the grain were always those of the female 
parent in the first generation, because these two characters are 
dependent on non-hybrid characters, the form and size of the 
ovule and ovary. In later generations they were intermediate 
in form. 
