440 THE AMERICAN NATURALIST. [VOL. XXXVIII. 



central bodies have been reported most investigators are agreed 

 that they are only granules without regularity or special signifi- 

 cance. They are no longer believed to be centrosomes. Fibrillae 

 are developed from the kinoplasmic caps and grow out against 

 the nuclear membrane and finally enter the nuclear cavity to form 

 the spindle. A large part of the substance of the kinoplasmic 

 cap is transformed into these spindle fibers. 



Papers by Schaffner ('98) on Allium and Fulmer ('98) on the 

 seedling of the pine are the last attempts to bring the centro- 

 some into the history of spindle formation in vegetative tissues 

 of higher plants. But their results cannot stand against the 

 accumulation of studies which indicate that centrosomes are not 

 present in the cells of any plant above the thallophytes with the 

 possible exception of the mysterious blepharoplast and certain 

 structures appearing in some phases in the life history of 

 Hepaticae. Centrospheres are unquestionably present in the 

 Hepaticoe and centrosomes have also been reported. The 

 centrospheres are, however, so generalized as to approach the 

 kinoplasmic caps in structure and development and it seems 

 quite possible that they are the forerunners of this manifesta- 

 tion of kinoplasm. The so-called centrosomes of the liverworts 

 do not exhibit the specialized structure or behavior of cen- 

 trosomes among the thallophytes and it is probable that they 

 are only smaller and somewhat more clearly defined centro- 

 spheres. These structures in the Hepaticae seem to hold an 

 intermediate relation between the definite kinoplasmic bodies 

 (asters, centrosomes and centrospheres) of the thallophytes and 

 the remarkable kinoplasmic activities in higher plants which 

 reach their highest expression in the processes of spindle forma- 

 tion in the spore mother .cell. These topics will be treated in 

 Section VI. 



Structures resembling kinoplasmic caps have been reported in 

 several other tissues than those noted above. Thus Murrill 

 (:oo) finds in the formation of the ventral canal cell of Tsuga a 

 dense fibrous accumulation beneath the nucleus which develops 

 one pole of the spindle in essentially the same manner as other 

 polar caps. The other pole of the spindle in this case appears 

 to be formed differently for the fibers seem to be intranuclear. 



