THE 
HEW PHYTOliOGIST. 
Vol. t., No. 5. May i6th, 1902. 
SOME RECENT WORK ON HYBRIDS IN PLANTS. 
By V. H. Blackman. 
(continued from page 80.) 
Correns’ ( 1901 , a, b) recent work on hybrids between the 
various constant races of Zea Mays has led him to put forward 
a classification of the various pairs of differentiating characters of 
a hybrid. He points out that the pairs of characters fall roughly 
into four groups according to their behaviour (1) during vegetative 
development, ( 2 ) during the formation of the sexual cells. In the 
vegetative development of the hybrid one of the characters may be 
dominant, the other recessive, as in the case of many characters of 
Pea hybrids already described ; to such a pair of characters he 
applies the term heterodynamic : or both characters may exhibit 
themselves in the hybrid and form a new character intermediate 
between those of the parents; such pairs of characters are found 
very commonly, and Mendel showed that they occur in Hieracium 
hybrids ; to these Correns applies the term homodynamic. Again 
there are also two extreme cases to be considered in relation to the 
behaviour of the characters at the time of gamete formation ; the 
characters may then be separated as described in the case of Pea 
hybrids; to these the term schizogonous (isogonous, De Vries) is 
applied; on the other hand the characters may undergo no separa- 
ration, and such pairs of characters are described as homoiogonous 
(anisogonous, De Vries). Four types may now be distinguished, as 
is clear from the table below. 
V KG KT ATI VIC DE VE LOPM E N T 
GAMETE FORMATION. 
TYPE. 
1. 
2. 
Heterodynamic. 
Heterodynamic. 
schizogonous. 
homoiogonous. 
Pisum. 
3- 
Homodynamic. 
schizogonous 
Zea. 
4- 
Homodynamic. 
homoiogonous. 
-- -:-it 1 ■ *—I'M » t 1 --■ -—-il' * | — 
Hieracium. 
