Spindle and Cytoplasm 73 



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A oreater concenii aiion is necessary to destroy the more adxanced 

 spindle, i.e., at anaphase, than a spindle at an early stage, pro-nieta- 

 phase. (3) The loini ol a particidar spindle is directly related to the 

 characteristic t\pe of nietaphasic pattern thai \vill develop alter treat- 

 ment such as the star, multiple star, ball, ex])lotled. or other arrested 

 metaphase.-''^ Configtn^ations dejjend uj^on stage at time of treatment, 

 concentration, and duration ot treatment or recover). 



Alter sober reflection upon these conclusions no one can disregard 

 the importance ot a specific concentration, ihe tyj^e ot cell, and, most 

 interesting of all, the particular mitotic stage at the time the drug 

 enters the cell. Specificity between chemical and spindle fiber is sup- 

 ported b\ these in\estigations. 



3.5— 2; 'Stamina] hair cells of Tradescantia. Techniques with the 

 Tradescautia material were used quite as effectively as \\'n\\ the neuro- 

 blastic cells just re\ iewed. The central feature and main advantage 

 lie in the possibilit) of applving colchicine at a particular stage and 

 following the progressi\e develoj^ment of mitosis thereafter. Trades- 

 cantia staminal hair cells ha\e been a faxorite material ior mitotic 

 studies in vivo for a long time. The first studies to be conducted with 

 colchicine and plant cells were accomplished with the stamina! hair 

 cells.'- 



Colchicine aj^j^lied to a cell when the spindle was well de\eloped 

 stojiped further de\elopment and reduced the spindle within a short 

 time. A deformed atractoplasm ajjpeared in the cell after destruction 

 of fibers b\ the chemical. Stronger concentrations were necessary to 

 induce changes if the spindle was very far along in development. 

 As the drug began its actifni, Brownian mo\ement on the spindle 

 was increased, indicating that the colchicine was acting u})on the 

 fibers. This action took place suddenh, as the chemical reached 

 the cell. 



Pliragmoplasts, which are spindle materials of cytokinesis, were 

 stopped in their further development and also reduced by colchicine. 

 A cell wall partly de\ eloped from each side of the cell can be stopjjed 

 by the drug. 



At metaphase, aclixity ujxjn the sjjindle is immediate. Die c-pairs 

 are formed as the spindle fibers are destroyed. Within 1 .S minutes, 

 grantdar changes upon the spindle showed that action had set in. 

 Within I hom^ and "iWi minutes, the entire grouj) of (hromosomes 

 retinned bv a j^recocious re\ersion to an intei j)hase. Such quick results 

 required strong solutions (2 per cent) . Generally, lesser concentrations 

 (0.05 per cent and 0.1 per cent) were used to elfect spindle lil)ers. 



Regardless of the stage from projjhase to anaj^hase, e\en as late 

 as the phragmoplast, an application of colchicine stopped mo\ement, 

 destroyed the spindle, and retinned the chiomosomes to interphase 



