288 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



to study the biological significance of calcium carbonate as a factor 

 in the occurrence of Calluna, and to ascertain whether the facts obtained 

 might throw light on the question of calcicole (" lime-loving ") and 

 calcifuge (" lime-hating ") plants in general. 



Pot cultures showed that Calluna grows normally in soil from a 

 typical heather area (" heather soil "), abnormally in soil directly 

 overlying chalk ("down soil"). In the latter case abnormality of 

 growth was shown by reduced germination capacity, retarded germina- 

 tion, arrest of root and curvatures of the growing region, arrest of 

 shoot, and small size and red coloration of the leaves ; also with these 

 abnormalities was associated the presence of colonies of bacteria on 

 the roots, and marked diminution of vigour in the growth of the 

 mycorrhizal fungus. The growth abnormalities can be induced in 

 seedlings growing in heather soil by watering with extracts of the 

 down soil ; the unfavourable factors are evidently of a chemical 

 nature. Culture experiments showed that the development of the 

 fungal and bacterial elements associated with the seed-coat is deter- 

 mined qualitatively by the nature of the soil extract used ; with 

 extract of heather soil the mycelial constituent is predominant, with 

 a down soil extract bacterial colonies form the prominent feature. 

 Sterilized seedlings germinated and for a time grew normally, but in 

 the absence of infection the root soon showed complete arrest of 

 growth and the seedlings died. The relation between Calluna and 

 its mycorrhizal fungus is apparently obligate, and successful growth 

 of the plant is ultimately dependent on infection of the roots at an 

 early stage by the fungus and the subsequent healthy growth of the 

 latter ; hence the soil preferences shown by the plant depend on the 

 maintenance of a biological balance between the roots and the con- 

 stituents of the micro-flora which beset them. — F. C. 



Inheritance of Flower size. By E. M. East (Bot. Gaz., pp. 177- 

 188 ; March 1913 ; with 4 plates). — The author used for his experi- 

 ments Nicotiana Forgetiana, Hort. Sand., and N. alata grandiflora. 

 Both species are almost always naturally self-fertilized. 



The first-named species has a mean corolla length of 25*6 mm. 

 When crossed with the latter (mean corolla length 78-8 mm.), the first 

 generation had a mean variability of 44*3 mm. This Fi generation 

 had very small, but the F2 generation (by fertilization of Fi inter se) 

 had great variability. The author considers that this result coincides 

 with expectation, supposing no dominance and four cumulative but 

 independent pairs of unit factors. 



The author assumes that the effect of environment on the size of 

 the corolla is so small as to be negligible. 



There is nearly perfect correlation of corolla length with style 

 and filament lengths, and a 61 per cent, average correlation of length 

 with breadth. The range of fluctuation in length is twice as great 

 in the larger-flowered species. — G. F. S. E. 



