REDUCTION IN THE PLANTS 



197 



Strasburger's hypothesis is, however, open to a very serious a 

 priori objection, as Hacker has pointed out ; for if the account of 

 "reduction" in the plants given by Guignard and Strasburger be 

 correct, it/corresponds exactly to the " pseudo-reduction " in animals, 

 and the " chromosomes " of the sexual generation must be bivalent 

 like those of the early germ-cells in animals. The recent observa- 

 tions of Belajeff, Farmer, and especially those of Sargant, give, how- 

 ever, good reason to believe that both Guignard and Strasburger have 

 overlooked some of the most essential phenomena of reduction. 

 These observations have not yet revealed the exact nature of the 

 process, yet they show that 

 the first division of the pollen- 

 mother-cells (in the lily) is of 

 the Jicterotypical form ; i.e. 

 that the chromosomes have the 

 form of rings. It is impos- 

 sible to avoid the suspicion 

 that these rings may be of 

 the same nature as the ring- 

 shaped tetrads in animals, 

 though apparently they do 

 not actually break up into 

 a tetrad. Until this point 

 has been cleared up by fur- 

 ther investigation the nature 

 of reduction in the plants 



Fig. 98. Division of the chromosomes (? tetrad- 



remams an Open question. formation) in the first division of the pollen-mother- 

 Belajeff and Farmer showed cell of the lily. (a. b. after FARMER and MOORE; 



c-g. after SARGANT.) 



that as the daughter-chromo- 

 somes diverge after the first 

 division they assume a V- 

 shape, and Miss Sargant's 



a. b. Two stages in the ring-formation (hetero- 

 typical mitosis), c-f. Successive stages, in profile 

 view, of the separation of the daughter-chromosomes. 

 g. The daughter-chromosomes, seen en face, at the 

 moment of separation ; this stage is perhaps to be 



Very interesting observations inter P reted as a tetrad like those occurring in the 

 . salamander. 



give some reason to believe 



that the V breaks at the apex precisely as described by Hacker in 

 Cyclops and vom Rath in the salamander (Fig. 98, g). Should this 

 prove to be the case the way would be opened for an interpretation 

 of reduction in the plants agreeing in principle with that of Riick- 

 ert, Hacker, and vom Rath ; and as far as the plants are concerned, 

 the a priori objection to Strasburger's interesting hypothesis might 

 be removed. 



