226 BOTANICAL GAZETTE [march 



conspicuous during the growth of the blepharoplast , disappear as 

 the blepharoplast breaks up into granules. 



The two sperms are formed within the two cells resulting from the 

 division of the body cell. That this is the case is readily seen in 

 sections (figs. 28, 2Q, 32) . The relations are particularly clear in 

 fig. 29, in which t is the pollen tube, and w the wall of the sperm 

 mother cell. The figure shows the apex of the sperm with a small 

 portion of its large nucleus still surrounded by the mother cell. The 



mother 



fig 



formed 



mother 



mov 



1. The peripheral portion of the partition 

 between the two sperms breaks down, thus allowing the sperms to 

 move about within the old body cell. At this stage the term body 

 cell is not strictly correct, because the cavity now consists of the com- 

 bined areas of the two sperm mother cells. Since, however, the outer 

 wall is still the wall of the original body cell and there is no name for 

 the new cavity, we may refer to it as the old body cell. The wall of 

 the old body cell soon breaks down and the sperms escape into the 

 main portion of the tube. 



measure about 200 



and about 275 fi from apex to base. After leaving the tube, they 

 increase somewhat in size, reaching a diameter of 230 /* and a length 

 of 300 fi. Consequently, they are easily visible to the naked eye. 



The living sperm, as seen under the microscope, has a large gran- 

 ular nucleus, surrounded by a thin and almost colorless sheath of 

 cytoplasm, which is somewhat thicker at the spiral end. The nucleus 



perm 



(fig 



The movements of the sperms are easily observed by simpl} 

 mounting a piece of the nucellus with its pollen tubes. In addition 

 to the lighting from above, some light may be reflected up through the 



pollen chamber. 



(fig 



so transparent that they scarcely obscure the view. The cilia begin 



sperms 



attached to the stalk cell. The movement of cilia is accompany 



