448 BOTANICAL GAZETTE [may 



Knop's solution. — Toole and Tottinghams find that additions of FeCOH)^ 

 to Knop's solution greatly increases the growth of barley tops in it (21 day 

 cultures), while additions of carbon black depress the growth of tops and 

 additions of HzSiO^ have no effect. None of these additions affect the growth 

 of the roots. Part of the beneficial action of the Fe(0H)3 may be due to its 

 neutralizing action on the acids of the solution. It is interesting to note that 

 the higher additions of Fe(0H)3 removed 90 per cent of the phosphorus from 

 solution. 



In another piece of work, Tottingham* has shown that he can displace 

 more than 90 per cent of the MgS04 of Knop's solution with Mg(N03)2 without 

 interfering with the growth of red clover, a rather heavy sulphur requiring 

 plant. It is evident that some of the nutrients in the commonly used nutrient 

 solutions are far beyond the minimum concentration necessary to give the 

 plant its optimum supply, and that the so-called optimum concentration of the 

 solution is determined by other factors than optimum supply. The conditions 

 of and the mechanism for absorption from the soil (root hairs with their acid 

 pectic layer in contact with soil particles bearing certain nutrients in compounds 

 of low solubiHty) are quite different. Work with water cultures has established 

 some very fundamental principles in soil fertiUty (essential nutrient elements, 

 necessity of balanced solutions, etc.). It is a question how much more this 

 method alone is capable of adding to our knowledge of soil fertihty. In the 

 present concentrated nutrient solutions with which we are working we may be 

 mainly playing the toxic concentration of one salt against the toxic concentra- 

 tion of another in a way to get the least possible injury. — Wm. Crocker. 



Chromosomes in Carex. — Oogenesis and spermatogenesis have been studied 

 by Heilborn^ in several species of Carex, special attention being given to 

 chromosome numbers, which vary greatly in this genus. The gametophyte 

 numbers in the forms investigated are as follows: Carex pilulifera 8, C. erice- 

 tortim 16, C. digitata 24, C. caryophylla and C. flava 32. Juel had already 

 reported 52 for C. acuta, and Stout 37 for C. aquatilis. It is interesting to note 

 that C. pilulifera has the largest chromosomes, and that in species with higher 

 numbers the chromosomes are correspondingly smaller. Attempts to cross . 

 the various species have not yet proved successful, but the work is still in 

 progress. — C. J. Chamberlain. 



5 TooLE E. H., and Tottingham, W. E., The influence of certain added solids upon 

 the composition and efficiency of Knop's nutrient solution. Amer. Jour. Bot. 5:452- 

 461. 1918. 



6 Tottingham, W. E., Sulfur requirement of red clover plant. Jour. Biol. 

 Chem. 36:429-438. 1918. 



1 Heilborn, Otto, Zur Embryologie und Zytologie einiger Carex-P^xten. Svensk 

 Botanisk Tidskrift 12:212-220. _^"g^. 7-J.^. 1918. 



