IN THE TROPICS. 
V.-THE OBSERVATIONS OF CORRENS ON 
MAIZE AND OTHER PLANTS. 
Correns (In) distinguishes the following types of behaviour 
in cross-bred plants:— 
j. Vegetative 
Development. 
I-—Pisum type ... Heterodynamous 
II.— — ... Heterodynamous 
HI-—Zea type ... Homodynamons 
In the case of heterodynamous vegetative development 
there is dominance or nearly so of one of the characters 
concerned (Correns uses the term “ paarling”=allemorph). 
In the homodynamons case there is blending of characters, 
a phenomenon particularly well seen in crosses between 
races of maize having differently coloured endosperms or 
different shapes of grain. In the former example we are 
concerned with a special case, namely, that of xenia. But 
Correns has also shown that in the case of several races of 
plants with differently coloured flowers, the apparently hete¬ 
rodynamous heterozygote has really a colour almost exactly 
intermediate between those of the parents; a fact not 
readily distinguishable by the eye alone owing to the 
operation of Weber’s Law. For example, in the case of the 
hybrid between Hyoscyamus niger and H. n. pallidus, de 
Vries describes the colour of the former plant as dominant, 
whereas the colour of the flowers of the offspring is really 
intermediate, or even somewhat nearer to that of H. pallidus. 
Heterodynamous pairs of characters are only a limiting 
case of homodynamons pairs; and Correns suggests that 
the former term should be used when the offspring show 
more than 75 per cent, of the character of one parent. 
Millardet’s false hybrids constitute, according to Correns, 
another limiting case (dichodynamous) of homodynamons 
characters. In the series leading up to these, the mutual 
