1912] Goodspeed: Nicotiana Hybrids 125 



4. Description of the Nicotiana Flower 



In general the structure of the Nicotiana flower adapts it 

 unusually well for hybridization experiments. In the case 

 of N. acuminata the flower is amply formed — the corolla tube 

 never less than 1 cm. in length, the diameter of the tube from 

 2-4 mm. and varying in diameter of flattened corolla limb from 

 13 to 29 mm. in the fully opened flower (see plate 29). It is 

 vespertine in common with many species of Nicotiana, es- 

 pecially the white flowered forms. In the bud the limb of the 

 corolla is somewhat plicate. The anthers — with the exception of 

 the one standing lowest in the tube — are not shedding pollen 

 until the corolla lobes are fully extended. The fifth anther 

 stands 2-3 mm. lower in the tube than the others and is shedding 

 pollen first and just as the flower opens fully. I have observed 

 on many occasions that two or three hours may separate 

 the two conditions and, in the case of a flower that opens fully 

 and for the first time after dark, the anthers may not break 

 until the following morning. The two-lobed stigma is receptive 

 from six to eight hours before the flower in general is in 

 anthesis and continues receptive for a considerable time after 

 all the anthers are open. A castrated flower under the bag may 

 be successfully pollinated toward the end of the bud stage or 

 while the corolla lobes are still folded and during the middle 

 of the day when the other flowers on the plant are completely 

 closed and deflexed. There is no difficulty in self-fertilization 

 naturally or under experimental conditions. It perhaps takes 

 place naturally when the flower closes during the middle of the 

 day. The corolla will withstand considerable mutilation and 

 still persist otherwise normally. I have never observed that the 

 buds are perforated or entered by insects nor that the plants in 

 general were injured in any way by insect pests. It has been 

 impossible to determine whether cross pollination is, under 

 natural conditions, effected by outward agencies and, in the 

 case of such a white vespertine species, this undoubtedly takes 

 place at night, if at all. 



