DEVELOPMENT OF PLANTS 



253 



The spore-producing hyphae in the young aecidia form a rather 

 loose stratum of somewhat elongated cells (Fig. 1 62 , A , I ) . These 

 cells divide, forming an upper series of cells which are smaller 

 and narrower than the lower or basal cells. These upper cells are 

 sterile, ultimately disappearing, and they have been compared 



f. 



FIG. 162 A. Spore formation in a cluster cup: I, appearance of the hyphae 

 in a young cup. 2, one of the cells from Fig. i, after it has divided into 

 the sterile cell and the large basal cell. 3, early stage in the fusion of the basal 

 basal cells of two adjacent hyphae. 4, the two nuclei of the fused cells have 

 divided and two of them are passing to the base of the cells and two into the 

 fused region of the cells. 5, the upper portion of the fused area is cut off, 

 forming the spore mother cell. This cell will divide once, forming a spore 

 and a small sterile cell. 6, a chain of spores and sterile cells is being formed 

 as noted in 5. After Christman. 



to remnants of the tubular outgrowth of the female gametangium 

 noted in the red algae. 



The basal cells enlarge, become inclined towards one another 

 in pairs and finally meet at their upper ends, the walls dissolving 

 at the point of contact. The nuclei of the two cells now pass 

 to the fused region of the cells and divide, forming four nuclei. 

 Two of these wander back into the base of their respective cells, 

 while the other two pass to the upper portion of the fused area 



