432 



MINNESOTA BOTANICAL STUDIES 



in shape and size, according to Reed,* while in Yucca glaiica the 



latter are distinguished from the former by their greater size, fewer 

 and larger nucleoli, less dense nuclear contents, and greater tendency 

 to plasmolyze (fig. 21). Also, in V. filamentosa the second and 



third divisions in the germination of the functional megaspore 

 occur at the antii)odal end (Reed'*), but in V. glaiica they occur at 

 the two ends (figs. 25-29). 



TABLE I 



RECORD OF NUMBER OF TIMES THAT EACH IMPORTANT STAGE 



WAS OBSERVED 



Numlier of 



N'uinber of flowers from 



structures which the 



seen in the structures 



Kind of .Structlt.e stage came 



Ovule with hypodernial initial cell m* 5 



" " initial divided m 10 



" " spore mother-cell enlarging and integuments evident.... m 12 



" " reduction division 33 6 



Preceding with number of chromosomes evident 4 3 



Ovule with four megaspores 101 10 



AH in one row 16 5 



Micropylar pair side by side 64 7 



Middle ones side by side 12 5 



Ovule with three megaspores during or after disintegration 52 7 



Functional megaspore at antipodal end 14 5 



" " at micropylar end 12 3 



" in middle 13 5 



Embryo sac with two nuclei 56 5 



" four " 95 6 



" eight " 12 3 



" " " two polar nuclei fusing or about to fuse at 



chalazal end 21 4 



Embryo sac with seven nuclei 85 8 



Pollen reduction-division prophases m 8 



" " " nietaphases m 2 



" " " telophases 6 2 



Pollen grains grouped by fours m 6 



" " separate, one-nucleate m 14 



" " two-nucleate m 1 



" " after germination m / 



Embryo sac with two male nuclei 3 3 



" " " one male nucleus, before or during its fusion 



with fusion nucleus 4 2 



Embryo sac with pollen tube, free endosperm nuclei, and egg 



undivided 94 10 



Embryo sac with proembryo 30 6 



" " walled endosperm cells and embryo 11 5 



Mitosis of sporophyte cell with twelve chromosomes evident 23 1 



" " endosperm cell with 18 chromosomes evident 20 2 



With at least 15 and possibly 18 27 2 



*m = manv in each flower. 



