59 



The literature gives conflicting reports regarding seed pro- 

 duction in H. flava. Some investigators have reported plants 

 of it to be self-fertile, others have reported the plants they have 

 studied to be self-sterile. Both self-compatible and self-incom- 

 patible plants have been found among plants of this species 

 grown in the New York Botanical Garden. Such conditions 

 are often seen in a species in which self-incompatibility is pres- 

 ent, especially if the species is propagated by seed (Cichorium 

 Intybus, Nicotiana Forgetiana, Eschscholtzia californica, 

 Brassica pckinensis, Brassica cliinensis, and others). The most 

 highly self-compatible plants produce pods in abundance, but 

 in them are many shrivelled ovules in which fertilization may 

 not have occurred and seeds in various stages of embryo abor- 

 tion together with seeds that are fully matured and viable (Fig. 

 3). This condition is also specially characteristic of plants that 

 are not fully self-compatible. 



A third species, H. Thunbergii, has in the author's experience 

 proved to be only feebly self-compatible. Very many carefully 

 made self-pollinations fail (see 6. 7 and 8), but many pods do 

 mature and these contain some seeds which will germinate. 

 All the plants of this species which are growing in the New 

 York Botanical Garden have behaved quite the same, but these 

 may have all descended from a single parent through vegeta- 

 tive propagation. A wide range of self-compatibility may be 

 exhibited by the seedlings which are to be tested as soon as 

 they bloom. 



The type of sterility in these species is, undoubtedly, that 

 of physiological incompatibility operating between the organs 

 concerned in sexual reproduction. The readiness with which 

 these species propagate from pieces of the roots and by rhizomes 

 has practically eliminated the use of seeds in commercial propaga- 

 tion. Such a method tends to perpetuate the grade of self-com- 

 patibility of the original plant which was used. It is possible that 

 the plants of the single-flowered type of fulva now growing in 

 America and Europe may have all come by vegetative propa- 

 gation from a single plant which happened to be fully self-in- 



