194 University of California Publications in Botanij [Vol. 5 



detected. Of the 100 capsules (above mentioned) that werf 

 examined in this way 34 only contained no well-formed seed, 

 while two contained 31 seeds each and a number over 20 seeds 

 each. This seed was, as above stated, produced from unprotected 

 flowers, but there is little reason to suppose that only those 

 ovules matured which were fertilized by foreign pollen. The 

 various hybrids differ among themselves as to the amount of 

 pollen which an individual flower produces and in no case does 

 it approach in amount that which is normal for the parental 

 species. Sufficient is produced, however, so that in the case of 

 60 protected flowers examined just after the anthers were open 

 the stigmas in 52 cases were covered with pollen. The crosses 

 back upon the parents in which the F^ hybrids are the male 

 parents have been recently made and may give results, in con- 

 nection with the amount of seed produced, which bear on this 

 point. The hybrid inflorescences also are very dense and the 

 flowers are produced in great profusion, so that in general the 

 chances are greatly in favor of unprotected flowers being self- 

 ( close) pollinated or pollinated with pollen from other flowers 

 on the same plant. The parental species are usually recognized 

 as normally self-fertilized and no visible methods are present on 

 the hybrids made between them to prevent self- and favor cross- 

 pollination. Seed has not at this date matured under bag. In 

 the case of the cross N. Tabacum var. macrophylla X N. sylves- 

 tris (H38) within each of over 30 bags containing from 30 to 50 

 flowers and buds an average of two maturing seed capsules can 

 be seen through the paraffine bag to be persisting. In such cases 

 the calyx is beginning to turn brown and the period during or 

 before which the F^ hybrid flowers generally fall has passed. 

 In the case of the crosses H35 and its reciprocal H40 and H41, 

 less than 20 maturing seed capsules,- in a total of over 75 bags, 

 seem to be persisting at this date. In general, however, it is 

 plain that a small amount of viable seed is produced by hybrids 

 of N. sylvestris with various N. Tabacum-Yavieiies and there 

 appears to be little doubt but that normal plants can be matured 

 from the seedlings developed from such viable seed. 



In connection with the seeding character exhibited by the 

 above hybrids and especially by the F^ plants of the cross N. 



