The Cellular Basis of Growth 51 



factors. Steward (1958) finds that in cells freely suspended in culture the 

 planes of division are highly irregular and unpredictable, since such cells 

 are not subject to the organizing restraints that are operative in the nor- 

 mal plant body. 



The forms of most plant structures are presumably related to the planes 

 in which their constituent cells divide. In a few cases this relationship has 

 been demonstrated. Thus in ovary primordia of elongate gourds such as 

 Trichosanthes and the "club" variety of Lageruiria, Sinnott ( 1944 ) meas- 

 ured in the growing ovary the angles between the mitotic spindles and 

 the longitudinal axis of the primordium and found that there were many 



45° 

 Anaphase 



0° 



O. 



45° 

 Telophase 



90° 



Fig. 3-18. Angles between mitotic spindle and ovary axis in metaphases, anaphases, 

 and telophases in Trichosanthes, the snake gourd, where the great preponderance of 

 divisions are transverse and thus predictable as to orientation. The mitotic figure evi- 

 dently becomes more stabilized in direction as mitosis proceeds. ( From Sinnott. ) 



