132 



"There is some reason for tlie failure of sweet potato fruits to 

 set (luring a i)art of the flowering period. We frequently see 

 Hcnvers as earlv as October and there is an abundance of them 

 through December and January but seed seldom set before Feb- 

 ruar\-. The sweet potato is flowering freely at this time but so 

 far i ha\ e failed to ol)serve any fruits starting to set. I have not 

 attempted any controlled pollination work excepting that of last 

 February. 



"With the exceptions of the numbers 311 and 314 all seedlings 

 were developed from .seed of the three varieties Bigwig, I'lackrock, 

 and Key West Yam, when grown in adjacent plantings, and it is 

 thought that these varieties crossed freely among themselves. 

 Numbers 311 and 314 are Wrenchy seedlings and are thought to 

 have resulted from natural self-pollinations as the .seeds were pro- 

 duced on a planting that was isolated from other varieties. As 

 close breeding might have a bearing upon sterility, the female 

 parent of the different seedlings used in this work is given in all 

 cases in wliich this is available." 



In a most recent letter from Professor Thompson it is stated 

 that the blooming season of 1925-1926 has thus far been unfavor- 

 able to the flowering of sweet potatoes and that for a large num- 

 l)er of varieties the anthers have been imperfectly formed and the 

 pollen apparently worthless. 



It is of interest to note that the summar_\- of the pollinations 

 made at St. Croix show s that 23 different cross-combinations were 

 tested, in\()lving fcnir named \arieties and various seedlings. In 

 one cross (Blackrock x Key West Yam) 76 tiowers were polli- 

 nated but only two yielded capsules. The highest percentage of 

 successes was had from crossing a seedling with the variety Big- 

 wig; of the fifteen fiowers cross-pollinated 8 capsules and 13 seeds 

 were obtained. Several combinations failed completely and in 

 one as man\' as 62 flowers \\ere invoKi-d. In most cases rather 

 few flowers set seed Ijut a tcjtal of 34 cai)sules and "j"; seeds were 

 obtained, all from cross-pollination. 



Seed obtained at Tin: Xi.w ^'ouk Botanical Garden 

 i)uring tlu' w intt-r of i<>24-l(j25 the flowering of sweet ])otato 

 plant- in a greenhouse at The New ^'()rk r.otanical ( iarden made 

 controlk-d cross-pollinations possible and fiom sonu' of the com- 

 binations capsules and seeds wrre obtained. 



These plants were grown a> f()llow>. L utlings were niade in 

 the spring of KJ24. The \-oung plants grew rapidly and were 



