72 



MORPHOLOGY OF THE CELL. 



240. As appears from 

 the following figures, the 

 first stage in the devel- 

 opment of an ordinary 

 stoma is the separation 

 of a part of an epider- 

 mal cell by means of a 

 vertical partition, thus 

 forming the mother-cell 

 of the stoma. This 

 next divides by a verti- 

 cal plane which soon 

 exhibits a narrow chink. 

 The cells thus slightly separated at their common wall may 

 by subsequent growth 

 bring about changes 

 in the relations of the 

 neighboring cells. 



In Sedum, as shown 

 by Strasburger, there 

 are preparatory divi- 

 sions in different di- 

 rections, while in 

 some monocotyledons 

 there are simultaneous 

 divisions in contigu- 

 ous epidermal cells. 



241. Stomata are 

 not present, at least 

 in a perfect form, in any submerged plant. In aquatics with 



FIG. 52. Vertical section of stoma of Hyacintkus orientalis. (Strasburger. ) 

 FIG. 53 a, 6, c. Three stages in the development of the stomata of Sedum spurium. 

 Pig. 53c shows the narrow slit made by the neighboring epidermal cells. (Strauburger.) 



