FIELD CEOPS. 335 



should be to have the huller so constnietea ami so operated as to reduce the 

 l»ropor(ioii of hard seeds to the greatest possible extent and at the same time 

 io break the smallest possible number of seeds." 



Improvement of the flax crop by propagation from selected plants, H. 

 HuNTKK {Dept. Agr. and Tech. Imtr. Ireland Jour., 15 {1915), No. 2, pp. 237- 

 246, pi. 1, fig. 1). — From experiments conducted to study some factors to con- 

 sider in the improvement of flax " it has been shown that flaxseed may be 

 artificially dried within certain limits of temperature without impairing its 

 germination. 



" Flax has been shown to be a self-fertilizing plant, directly by artificial 

 means and indirectly by the cultivation of the seed of single plants, which was 

 found to exhibit all the characteristics of limited variability of self -fertilizing 

 plants when treated in a similar manner. This leads to the conclusion that the 

 basis of the selection of parent stocks should be single plants and not groups 

 of plants. 



" Seeds of a self-fertilizing plant, when sown under similar soil conditions 

 will demonstrate whether the characters for which the parent plant was chosen 

 are inherent or adduced by conditions peculiar to the conditions of environment 

 under which it was grown. Thus the true value of any selected plant must 

 always be determined finally by the character of its progeny. 



" The flaxseed in general cultivation is a mixture of many types, varying in 

 character and degree, which are readily capable of selection and propagation as 

 pedigreed cultures." 



Investigations on hops. — III, The pollination and fertilization processes 

 in Hamulus lupulus and H. japonicus, O. Winge {Conipt. Rend. Lab. Carls- 

 Iterg, 11 (lOlJf), No. 1, pp. 46, pis. 2, fiijs. 22). — This article continues the report 

 of researches previously noted (E. S. R., 31, p. 52G), and deals especially with 

 the pollination processes. The results of the investigations may be summed up 

 as follows: 



" Zinger's description of the formation of the embryo sack and the growing 

 together of the integuments in Humulus is correct, but the author is wrong in 

 his statement that the ovule lacks a micropylc, the presence of which has already 

 been determined by Lermer and Ilolzner. 



" The microspores are developed and ripen in basipetal order in correspond- 

 ence with the dehiscence of the pollen sacks by means of apical pores. It is not 

 easy to get the pollen grains of H. lupulus to grow en an artificial substratum, 

 but the pollen grains of H. japonicus grow willingly on a gelatin solution. The 

 pollen grains of H. lupulus retain their power of growth for three days on 

 being kept in a dry room of the laboratory. The tapetum in Humulus offers a 

 good example of multiuuclear cells and vegetative caryogamy, the original 

 divalent nuclei dividing rei^eatedly, after which the products of division con- 

 stantly fuse together. This gives rise to plurivalent, synkaryonlike nuclear 

 complexes. 



" Rosenberg and Bonnet's theory that the tapetum originates phylogenetically 

 from the archespore and consists of sterile archespore cells can not be accepted, 

 and for this reason it can not be admitted that atavistic tendencies give the 

 explanation of the multiuuclear condition of the tapetal cells. It is suggested 

 that the peculiar nuclear condition of the tapetum has a physiological explana- 

 tion, and the same applies to the eudospex'm's wealth of chromosomes. Both 

 tissues are to a very great extent connected with the nutrition, which must be 

 reflected in the abundance of chromatin. 



" The growth of the pollen tube in Humulus does not suggest true aporogamy. 

 as Zinger maintains. Zinger's description of the deep penetration of the pollen 

 tube into the integuments is somewhat exaggerated, especially in the case of 



