RECENT ADVANCES IN SCIENCE 49 



results. All the nuclei of the antheridium also degenerate 

 except one which, together with the greater part of the cyto- 

 plasm, passes through the fertilising tube to the oosphere. 



Dr. Weston describes Thraustotheca clavata, an aquatic 

 fungus belonging to the Saprolegniacece. The sporangiospores 

 are non-motile and escape by bursting the sporangium wall. 

 The zoospores are laterally biciliate and reniform in side view. 



Cytology. — Prof. Mottier deals with the origin of Chloro- 

 plasts and Leucoplasts which he regards as derived from 

 granular or rod-shaped primordia. These latter are con- 

 sidered to be permanent structures of the cell originating only 

 by division, and therefore ranking with the nucleus. As such 

 it is suggested they may share in the transmission of hereditary 

 characters. There are in addition similar bodies to those 

 which develop into plastids, and these chrondriosomes are 

 likewise regarded as permanent structures. 



Genetics. — The results of A. B. Stout's experimental breed- 

 ing of chicory show {Journal of Genetics, Feb. 191 8) that 

 self and cross-incompatibles occur, and that even after three 

 generations a self-sterile roce may still give rise to sporadic 

 plants which are self-compatible. The offspring of the latter, 

 however, do not breed true in this respect. The degree of self- 

 fertility varies and self-sterile individuals arise sporadically 

 from self-fertile parents. No simple Mendelian formula fits 

 the results obtained, which indicate a great variability in 

 hereditary transmission. 



PLANT PHYSIOLOGY. By Prof. V. H. Blackman, Sc.D., F.R.S., 

 Imperial College of Science and Technology, London. (Plant Physiology 

 Committee.) 



It is well known that in many plants there is a well-marked 

 antagonism between growth and reproduction. This is clearly 

 seen in the case of many fruit trees where the conditions which 

 lead to active vegetative growth may be inimical to the repro- 

 ductive processes. In such cases the reduction of vegetative 

 growth, as by root pruning, may bring about vigorous flower 

 and fruit production. The study of the effect of external 

 conditions on these two processes, growth and reproduction, is 

 obviously of great importance. In the case of the higher 

 plants, however, the difficulty of investigating such a problem 

 is increased by the close connection under ordinary conditions 

 4 



