424 SECTIONAL TRANSACTIONS.— K. 



the effect of zinc sulphate on Dwarf French Beans. The plants were sup- 

 pHed with varying concentrations of zinc sulphate ranging from one to 

 200 parts per million, ten to fifteen plants being used for each concentra- 

 tion. Conclusions were drawn from the appearance of the plants throughout 

 the experiments, and also from the dry weights of the plants at the end of 

 the experiments (twelve weeks). All experiments showed that the average 

 dry weight of the plants decreased as the concentration of zinc sulphate 

 increased. Plants were, however, able to survive for twelve weeks in con- 

 centrations as high as 50 parts per million, although they appeared to be 

 unhealthy. This is significant, as the concentration of zinc in this locality 

 is never as high as 50 parts per million. 



Dr. Winifred E. Brenchley. — Recent work on boron in relation to plant 

 disease (2.35). 



The importance of boron in the control of certain forms of plant disease 

 is now widely known, and the results of tests in many parts of the world 

 are being recorded with increasing frequency, from the scientific as well as 

 from the commercial aspect. 



The occurrence of heart rot in sugar beet was first noticed at Rothamsted 

 in 1935, the earlier sown crops being the more severely attacked. In the 

 autumn a number of healthy and diseased plants were transferred to sand 

 cultures with adequate nutrients, some receiving light or heavy dressings 

 of boric acid and others none. In the absence of boric acid the characteristic 

 signs of boron deficiency appeared in the shoots, the apices of the stems and 

 the flower buds blackening and dying. This occurred even when no 

 symptoms were present before transplanting. In the presence of boric 

 acid all plants produced healthy shoots, with no deficiency symptoms. 

 Where heart rot was originally present and the main axis killed, a number 

 of healthy, lateral shoots were produced. The later addition of boron did 

 not improve the condition of the roots of affected plants, as irremediable 

 damage had been done before transplanting. 



The ability to produce healthy shoots in the second year from affected 

 roots may be important for seed producers, if the use of small amounts of 

 boron compounds after the presence of the disease is recognised renders 

 seed formation possible. 



Miss I. M. Wilson. — The asci of Peziza rutilans Fries. (2.55). 



Peziza rutilans is a Discomycetous fungus in which sexual organs are 

 absent. The ascus is formed, as in many other Ascomycetes, from the 

 binucleate, penultimate cell of the crozier. Fusion of these two nuclei 

 takes place during the early stages of ascus formation. Successive crops of 

 asci are formed by the proliferation of the crozier. 



The first two divisions in the ascus constitute a meiotic phase. Sixteen 

 bivalents are present in the prophase of the first division and sixteen longi- 

 tudinally split V-shaped chromosomes pass to each pole in the anaphase. 

 In the prophase of the second division sixteen similarly split chromosomes 

 reappear, and in the anaphase sixteen V-shaped chromosomes travel to each 

 pole. The third division in the ascus is a mitosis. Sixteen V-shaped 

 chromosomes are found in the prophase and metaphase ; they split longi- 

 tudinally and sixteen V-shaped chromosomes pass to each pole during the 

 anaphase. 



Sixteen V-shaped chromosomes are also present in the divisions of vege- 

 tative nuclei and in the two nuclei which undergo a simultaneous mitosis in 

 the crozier of the ascogenous hypha. 



