624 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



stock or scion through a physiological disturbance, and the variegation 

 of leaves brought about by what the Germans call " Infektiose 

 Chlorase." If true hybrids can be obtained by grafting, either the 

 character-determining factors are not limited to the nucleus, but are 

 present in the cytoplasm as well, and able to pass through the connect- 

 ing strands of cytoplasm from the cells of one member of the graft into 

 the cells of the other, or nuclear fusion must take place between the 

 cells of the stock and scion. Light has been thrown upon the problem 

 of the apparent mixture of characters in the vegetative tissues without 

 a mixture of character factors in the reproductive cells by Baur's 

 work on the Pelargonium, where a variety with colourless leaves 

 grafted on a green variety has resulted in many adventitious branches 

 at the junction of the tissues of the two varieties with leaves of various 

 mixtures of white and green. The writer holds that this is not really 

 a case of a mixture of characters, but a mixture of the two different 

 tissues, each of which retains its individual characters, and that there 

 is no satisfactory proof that any modification or mixture of characters 

 brought about by grafting is transmissible through the germ plasm, 

 while the fact that cells of different species can enter into such close 

 union as they do in some of the so-called hybrids, and yet retain their 

 individual characters, is strong proof that the character-determining 

 factors are locked up in the nucleus and are only transmitted through 

 nuclear fusion. If we accept the criticism that a hybrid must contain 

 a hybrid germ plasm, then the existence of graft hybrids has not 

 been estabhshed. — A. P. 



Hops as Manure^ Spent {Jour. Bd. Agr. vol. xxi. No. 5, p. 439). — 

 Although spent hops are relatively poor in potash as compared with 

 well-rotted farmyard manure, in other respects the two manures are not 

 dissimilar in composition. Spent hops possess a considerable capacity 

 for absorbing moisture. As regards soil, they have been proved to be 

 an excellent manure on light and medium soils, and there is httle danger 

 of their making the land sour provided the soil does not become unduly 

 deple ed of lime. In particular spent hops would seem to make an 

 excellent mulch for fruit trees, &c. — A. S. 



Hybrids and the Mutation Hypothesis. By Edward C. 

 Jeffrey (Bot. Gaz. vol. Iviii. pp. 322-336, October 1914; 4 plates). — An 

 important characteristic of hybrids is that the spores are frequently 

 infertile or irregular. The author has examined spores and pollen 

 in a great number of plants. If malformation of spores involves 

 hybridization in the past, then it was found that not only Oenothera 

 but a whole series of other plants are probably hybrids. 



No evidence of hybridization (on the above reasoning) was found 

 amongst either liverworts or mosses except in the single case of 

 Sphagnum, nor amongst the Lycopodiales. 



Equisetum X littorale appears to be a cross E. arvense x limosum. 

 E. variegatum var. Jesupi is probably E. hiemale x E. variegatum. 



