306 



is less precision in llie difTerenl slages tlian in llie lielerotype. Tiie 

 partners of tlie bivalents are segmenled and Iheir halves pass to 

 the poles. The same behaviour is shown, in many cases, by the 

 descendants of the singles too. In the telophase a new eliniination 

 of the hist mentioned chromosome elements takes place, the foar 

 ordinary microspores (containing the descendants of the gemin 



Fig. 2. a. R. (Coriifoliae) *solanifolia Matss. Diakinesis showing 7 bivalent aud 

 21 unpaired chromosomes. b. R. glutinosa Sibth. & Sm. *libanofica Boiss. Meta- 

 phase showing 7 bivalents and 28 singles in the same plane. c. R. (Tomentosae) 

 *suhcristata Schz. Interkinesis after the heterotypic division showing two great and 

 some small nuclei. — Same magnification as in the first plate. 



thus obtaining only a few or sometimes none of them. In that 

 way, the chromosome nnmber of these pollen grains will be rather 

 small, sometimes only 7. All the other microspores — there arises 

 a great nnmber of them from each pollen nother cell — contain 

 only descendants from the univalent chromosomes, and their chro- 

 mosome nnmber then often will be still smaller. 



13. Some of the microspores, probably those containing the 

 descendants of the bivalents, develop into pollen grains and can 



