524 Cannon : Studies in Plant Hybrids : 



preparation. On the other hand instances were observed, hke/. 8, 

 in which a reticulum was being formed from the condition as just 

 described. The exact fate of the chromatin was thus not deter- 

 mined. 



The association of chromosomes in pairs in the early history 

 of the reproductive cells recalls the similar condition in animals 

 as given by Montgomery * and Sutton, f But the significance of 

 the association in hybrids is not entirely clear, since with Mont- 

 gomery's hypothesis in mind that in pure races the two chro- 

 mosomes of each pair are of different parentage, it seems difficult 

 to conceive of Sutton's as applied to hybrids, that the members 

 of each pair cover the same field of development ; because in hy- 

 brids the latter can only be true in a broad way, depending ap- 

 parently upon the affinities of the pure parents of the form. It 

 may be, however, that the differences between the chromosomes 

 of any pair in hybrids capable of forming functional spores are so 

 slight that union is possible even if the potentials of the chromo- 

 somes are not identical. 



After the sporogenous cells are cut off there ensues a long 

 period of growth during which the nucleus of the young spore 

 mother-cell undergoes characteristic changes. The chromatin of 

 the nuclear reticulum becomes gathered to one side of the nucleus 

 and the contracted condition known as sj-napsis results. The 

 preparation for synapsis takes place at an early time in the history 

 of the spore mother-cell, and the portions of the nuclear changes 

 resulting in synapsis which were seen may be briefly described. 

 The delicate reticulum which extends through the nuclear vacuole 

 of the resting nucleus becomes so changed that small masses of 

 chromatin of unequal form and size are found scattered along its 

 meshes, more especially in the peripheral part of the nucleus. 

 These masses are arranged in lines which often radiate from the 

 nucleolus as a center ; the linin threads which connect the masses 

 may be seen for a considerable distance from them extending into 

 the nuclear vacuole. From a position extending over the entire 

 periphery of the nucleus the chromatin becomes gathered to one 



* Montgomery, T. H. The heterotypic maturation mitosis in Amphibia and its 

 general significance. Biol. Bull. 4: 259. 1903. 



t Sutton, W. S. On the morphology of the chromosome group in Brachystola 

 7nag7ia. Biol. Bull. 4: 24. 1902. 



