[januayk BOTANICAL GAZETTE 60 



in the resting condition a fine chromatin network and a large, often 

 vesicular, nucleolus. After the fusion of the polar nuclei, which 

 occurs near the middle of the sac (fig. 25), the resulting endosperm 

 nucleus approaches the egg apparatus. At this time, as shown in 

 fig. 26, the endosperm nucleus still possesses two nucleoli, evidences 

 of its binucleate origin, and is considerably larger than the egg 

 nucleus. It is frequently in contact with the egg. There are 

 three very small but typical antipodal cells. 



The nutritive jacket surrounding the embryo sac of Verbena 

 usually consists of a single layer of cells derived from the inner 

 epidermal layer of the integument, and it develops especially at 

 the micropylar end, investing the egg apparatus of the embryo sac. 

 The cells of the jacket have conspicuous brownish contents, among 

 which are numerous starch grains. Rather frequently a portion 

 or portions of the jacket cells inclosing one or more grains of starch 

 protrude into the embryo sac. 



DEVELOPMENT OF MICROSPORES 



At the stage shown in fig. 14 the hypodermal archesporial row 

 is distinguishable, and the succeeding stages follow the usual course 

 of development (figs. 28, 29). There may be only a single longi- 

 tudinal row of spore mother cells, but one or two longitudinal 

 divisions of the primary sporogenous row may take place (rig. 30). 



The pollen mother cells within a loculus do not divide quite 

 simultaneously, so that several different stages of the reduction 

 division may be found among them (figs. 31-33)- It is rather 

 difficult to count the number of chromosomes in this species 

 (V. angustifolia) because they are remarkably small and slender, 

 but it was ascertained that 8 is the 2X number. In the second 

 maturation division the two spindles usually lie across each other 

 as in fig. 33. 



In V. angustifolia there are two different types of tetrad 

 formation. In the one case the peripheral cytoplasm of the pollen 

 mother cell is left over to form a wall for the tetrad, this wall 

 subsequently disintegrating (figs. 34, 35), while in the other case 

 the entire mother cell is utilized in the formation of the tetrad 

 (fig. 36). Figs. 37-41 give successive stages in the development of 



