Higher Allopolyploids 463 



bracteata X F. vesca rosea tetraploid hybrid with such a diploid 

 species as F. collina. At first metaphase in these triploids usually 

 ten bivalents and a univalent are found, which would undoubt- 

 edly indicate pairing between chromosomes that are not stricth^ 

 homologous. There are several possibilities in an allotriploid 



Fig. 134. Chromosomes in a triploid hybrid between Crepis capillaris 

 and C. tectorum. Left, diakinesis showing Ihree bivalents and four uni- 

 valents. Right, first metaphase showing the same configurations. (Re- 

 drawn from Hollingshead in University of California Publications in the 

 Agricultural Sciences.) 



whose three genomes are A A B. Although frequently the two A 

 sets pair and the B set forms univalents, sometimes the univalent 

 chromosomes of the B set pair with one another so that only 

 pairs or pairs plus one univalent are found. It is possible that 

 the B set would be sufficiently like the A's that an A and a B 

 set would pair, but in such a plant, trivalents would more likely 

 be formed and the plant would behave like an autotriploid. 



Higher Allopolyploids 



In some genera of plants allopolyploids with more than four 

 genomes are frequent. Often examination of the chromosome 

 behavior at meiosis would indicate that the plants were diploids, 

 for they form only bivalents, and it is only from further evidence 

 that we could detect that the plant is perhaps a hexaploid or 

 octoploid or some other type of higher polyploid. If the number 

 of chromosomes in such a plant is large, we might suspect an al- 

 lopolyploid situation, but even this is only suggestive. The pres- 



