32 Plant Tissue Culture 



which normal development and response were 

 maintained for considerable periods, were ob- 

 tained in a solution containing, besides the salts, 

 1 per cent dextrose plus 5 g. Liebig's meat extract 

 per liter. The work was well planned, excellently 

 carried out, and, as we can now see, of consider- 

 able promise, but no subcultures were attempted, 

 Haberlandt apparently overlooked its importance, 

 and no attempt seems to have been made to follow 

 it up. By one of those coincidences which often 

 crop up in science, Bobbins in the United States, 

 following the leadership of Jacques Loeb (Rob- 

 bins, 1939, 220; Loeb, 1915, 302, 1916, 23, 303, 

 1917, 304, 305, 1918, 306, 1924, 24) and Louis 

 Knudson (Knudson, 1916, 168, 1919, 100 ; Knudson 

 and Smith, 1919, 169), simultaneously and inde- 

 pendently carried out similar work with compar- 

 able results (Robbins, 1922, 57). His method dif- 

 fered from Kotte's chiefly in the use of yeast 

 extract in place of Liebig's meat extract. Rob- 

 bins (1922, 177) and his colleague, Maneval 

 (Robbins and Maneval, 1923, 59, 1924, 258) carried 

 their work somewhat further than did Kotte and, 

 by using subcultures, succeeded in maintaining 

 cultures for some 20 weeks. But in every series, 

 there set in a gradual diminution in growth rate 

 and all cultures were ultimately lost. The results 

 seemed to suggest that some unknown material 



