Varietäten, Desccndenz, Hybriden. 293 



by de Chamisso D. Purpuren heptandra , is characterised by the 

 dialysis and staminody of the petals. The degree to which the abnor- 

 mality is carried varies in different individuals and also in the dif- 

 ferent flowers of one Indivudial. In the most extreme form all the 

 petals are replaced by stamens. so that the flower, while apparently 

 lacking a corolla, possesses 9 (rarely 10) stamens. In the majority 

 of cases, however, the petals of the lower lip alone are replaced 

 by 3 stamens, thus making 7 stamens in all. Almost every stage 

 between the true he ptcmdra-CQXi&\\.\ox\ and the normal structure occurs. 

 It is only rare that all the flowers of a spike present a uniform 

 degree of abnormality ; more often they form a graduated series, in 

 which the dialysis and staminody gradually diminish with succeeding 

 flowers. The gradual return towards the normal type may be conti- 

 nued up to the apex of the spike, or it may reach its maximum at 

 a region some way below the summit and be followed by a gradual 

 decline towards the abnormal structure, ending in a return to the 

 heptandrous condition in the topmost flowers. There is some indi- 

 cation that the degree of heptandry may be influenced by external 

 conditions, at any rate by those of light and moisture. 



The distinction between the variety heptandra and the type is 

 sharply marked. The variety is recessive to the type and segregation 

 takes place in F 2 . 



So far as observations were made on the inheritance of colour, 

 thev entirely confirm the results of Keeble, Pellew and Jones 

 (New Phytologist, Vol. IX. p. 68. 1910.) 



In the course of the experiments two new forms appeared, viz. 

 one with stem and leaves nearly smooth, and one in which the 

 spots on the lower lip of the corolla had fused to form large blot- 

 ches. The inheritance of these characters is under investigation. 



R. P. Gregory. 



Saunders, E. R., Studies inthelnheritanceofDoubleness 

 in Flowers. I. Petunia. (Journ. Genetics, I. p. 57—69. with 7 

 flg. 1910.) 



In the double Petunia the corolla-tube is occupied by a number 

 of additional petaloid structures and stamens. Many of the additional 

 petaloid structures may bear anther-like structures and some have 

 been found with a structure like a Stigma. The gynaecium is always 

 malformed ; even when the ovary and Stigma have a normal exter- 

 nal appearance, the ovary is found to contain perianth-parts, stamens 

 with well-formed pollen and, in some cases, also ovules below or 

 among these other structures. All attempts to use the doubles as 

 seed-parents have proved fruitless; the double character can, there- 

 fore, only be introduced into the pedigree on the male side. 



Breeding experiments have given the following results: 



1. When a Single is crossed with a double, doubles as well as 

 Singles occur in the first (F x ) generation. 



2. When such F r singles are self-fertilized, or crossed inter se, 

 the resulting offspring are all Single. Doubles are, in fact, only 

 obtained when the pollen of doubles is used to fertilize the seed- 

 parent. 



3. The proportion of Singles in a mixed family probably always 

 exceeds the doubles, in ratios which approximate in various families 

 either to 3 Single: 1 double or 9 Single: 7 double. The occurrence 

 of the 9 : 7 ratio in some families strongly suggests that more than 



