No. 454.] STUDIES ON THE PLANT CELL. 735 



through multipolar stages and later become bipolar are called 

 multipolar polyarch spindles. When the spindle has a well 

 defined axis from the beginning, as is generally true of the cells 

 in vegetative tissues of higher plants, it is termed multipolar 

 diarch. Strasburger has shown that these types, while easily 

 separated in the extremes, grade into one another so that the 

 classification is not founded on distinctions of a very funda- 

 mental character. The spindle of Osmunda, for example, 

 resembles a multipolar diarch, but its method of development is 

 more closely related to that of other spindles in spore mother- 

 cells (multipolar polyarchs) than to those of vegetative tissues. 

 The gymnosperms offer in Larix an excellent subject for 

 studies on the formation of pollen, and this type has been 

 treated in several important papers, notably by Belajeff ('94(5), 

 Strasburger ('9S) and Allen ('.03). Belajeff's contribution is 

 important as the first investigation that considered the multi- 

 polar spindle as a preliminary stage in the development of the 

 bipolar structure. Other authors, at this time and previous to 

 his publication, had noted multipolar and tripolar spindles 

 (Strasburger ('80) and ('88) in several forms), but the Hly had 

 received the greatest attention in this connection (Farmer ('93) 

 and ('95<i), Strasburger ('95), Sargent ('97) and Mottier ('97) ). 

 Mottier's investigation presented the first detailed account of 

 spindle formation in this angiosperm and will be discussed 

 presently. 



Allen's (103) paper on Larix includes one of the best discus- 

 sions of ' the literature bearing on the subject of spindle forma- 

 tion that has yet appeared. He finds that the cytoplasm around 

 the nucleus just previous to mitosis comes to contain a loose net- 

 work of fibrillEe. Some of the fibers may be followed through 

 the nuclear membrane and may be seen attached to chromatin 

 bodies in the interior (Fig. i4«). Later the cytoplasmic fibrillse 

 become arranged radially and extend from the nucleus even to 

 the outer plasma membrane at the periphery of the pollen 

 mother-cell. The radiating fibers are connected with one another 

 by branches which indicate that the structure is in part an 

 expanded condition of the original network, but the fibers also 

 grow. The fibers now fold over so that they tend to lie parallel to 



