CYCADALES 



141 



tions of free nuclear division in Stangeria will show that the nuclei 

 in the upper part of the embryo, during the earlier mitoses, may be- 

 come much more numerous than in the lower part. 



... :,.< y. "^ -■ t^ t .•tt-s .. - -^ »^A i.'\^^ ^ 



Fig. 152. — Zamiafloridana: photomicrograph of a small portion of a section showing 

 an early free nuclear division; X413. Negative by Miss Ethel Thomas. — From Cham- 

 berlain, Methods hi Plant Histology (5th ed.) (University of Chicago Press). 



During the earlier mitoses, the spindle fibers and polar radiations 

 are very striking, but there are no centrosomes at any stage (fig. 



152)- 



The number of nuclei reached in the free nuclear period varies. 



