176 



THE POPULAR SCIENCE MONTHLY. 



,- M. 



*- 'P^> /Zl '*-> 



position, as *i rule, is accomplished in some other flower than that 

 from which the pollen was gathered, and that cross-fertilization 

 is thus secured. 



Once fully equipped with this important commodity, she may 

 be seen either crawling over or resting within the flower, gener- 

 ally with the head toward the base. From 

 time to time she makes a sudden dart and 

 deftly runs around the stamens, and anon 

 takes a position with the body between and 

 the legs straddling two of them, her head 

 being usually turned toward the stigma. As 

 the terminal halves of the stamens are al- 

 ways more or less recurved, she generally 

 has to retreat between two of them until the 

 tip of her abdomen can reach the pistil (Fig. 

 7). As soon as a favorable point is reached 

 generally just below the middle she rests 

 motionless for a short time, when the abdo- 

 men is slightly raised and the lance-like ovi- 

 positor is thrust into the soft tissue, held 

 there the best part of a minute, while the 

 egg is conducted to its destination, and then 

 withdrawn by a series of up-and-down mo- 

 tions. Fig. 8 is a transverse section of the 

 young fruit at this stage of the growth, in- 

 dicating the manner in which it is punct- 

 ured at a, <x, and how the egg is conveyed 

 into the ovarian cell at b, while Fig. 9 shows 

 a longitudinal section of the pistil at a, the 

 puncture of the ovipositor at b, and the 

 egg within the ovarian cell at c. 



The stigmatic liquor is not nectarian, and the flower secretes 

 but a small amount of nectar at the base of the petals ; and while 

 these facts serve to disprove any positive value of their nectar in 

 the pollination of the yucca flowers, they add to the importance 

 of Pronuba by showing that the acts of collecting pollen and 

 transferring it to the stigma do not result in any food compensa- 

 tion, as I was at first inclined to suppose. In other words, there 

 is no nectar to allure other nectar-loving insects and cause them 

 to go to the stigma ; but, on the contrary, those which are drawn 

 to the plant by the slight amount of nectar are led in the very 

 opposite direction, viz., to the base of the style or of the flower. 

 It is also an interesting fact that I have never noticed Pronuba 

 feeding, as contradistinguished from pollinizing, for the motions 

 of the tongue of Lepidoptera when feeding are quite character- 

 istic and easily recognized. Indeed, the two pieces which form 



Fig. 6. Pronuba tdccasel- 

 la, female, in the act of 

 gathering pollen from the 

 anthers ; five times en- 

 larged. 



