100 



Pecan-Growing 



centage of the stigmas of the pistillate flowers have dried or 

 calloused before the pollen is shed, thus precluding fertiliza- 

 tion with their own pollen (see Fig. 23). 



In size, shape, and general characters, the pollen of the 



two groups of var- 

 ieties differs little, 

 but the variation 

 lies in the time of 

 rapidity of the pol- 

 1 e n development. 

 In general pecan 

 pollen is somewhat 

 flattened or sphe- 

 roidal in shape. It 

 is rather large in 

 comparison with 

 pollen from other 

 nuts, being of prac- 

 tically the same 

 size as that of 

 hickory, consider- 

 ably larger than 

 pollen of Japan 

 walnuts, and much 

 larger still than 

 that of the Spanish 

 chestnut. Pecan pollen-grains have from three to five germ- 

 pores, and usually in germinating send out a tube through 

 one pore. However, sometimes the pollen-grains send out 

 more than one tube. The catkins of staminate flowers mature 

 and begin shedding pollen first at the basal end, proceeding 



Figure 23. — Pistillate and staminate flowers 

 of a pecan tree representing group //. The 

 stigmas had dried and nut growth started 

 before any pollen had shed from any of the 

 catkins on the tree. 



