876 



VEGETABLE GKOWTH. 



998. Development of stomata. Each of the mother-cells from 

 which the guardian- cells of stomata are formed contains at first a 

 large nucleus with one large nucleolus or several small nucleoli 

 (Fig. 164, No. 1). The nucleus grows in size and becomes gran- 

 ular, but does not lose its identity in the protoplasmic mass (Fig. 

 164, Nos. 2, 3). At this period faint stripes appear w 7 hich con- 

 verge towards the poles of the spheroidal nucleus, while there is 

 developed midway, at what has been well called the equator, a 

 row of granules lying in one plane and forming a sort of disc 

 or plate (Fig. 164. No. 4). The granules next pass for the most 

 part in the meridian lines towards the poles, and there accumu- 

 late to constitute new nuclei (Fig. 164, No. 5). The polar masses 



:-.y 



164 



are connected by faint stripes, and from this stage (Fig. 164, 

 No. 6) go rapidly to their fuller development. In them rods 

 appear which, though somewhat curved, generally lie in the 

 direction of the axis of the spindle, and the contour of the two 

 masses becomes clearry defined (Fig. 164, No. 7). Next, the 

 faint stripes thicken somewhat, while at the equator there is 

 developed a plane of minute granules (Fig. 164, No. 8), which 

 become confluent and form a coherent film. This soon splits 

 into halves between which cellulose is secreted. At first the 

 secretion takes place in spots, but it soon becomes uniform. 

 The splitting of the film for the formation of the cellulose is 

 similar to that of the nuclear disc, except that in the former the 



FIG. 164. Changes in the nucleus during cell-division in the mother-cell of a stoma 

 of Iris puraila. The dark parts in all the figures represent the nuclein. In No. 9 

 the cell-division is complete. (Strasburger. ) 



