1902] CUR REN T LI TERA TURE 2 4 1 



as the vegetative substance of the cell, the chromatin granules as the highly 

 specialized hereditary substance, and the linin as an intermediate substance 

 which transmits hereditary peculiarities in a slow degree from the cytoplasm 

 to the chromatin, and that the linin is in part the bearer of hereditary quali- 

 ties. He considers that undue prominence has been given to the chromatin 

 granules as the bearers of heredity. He thinks more light would be thrown 

 on the tropisms if the cytological changes that originate or accompany them 

 were accurately determined. He believes that the only correct guide to the 

 evolutionary affinities of the plant groups and the development of species 

 within these groups is to be found in the study of the morphological details 

 of varieties and species based on the cell as the ultimate factor; also that it 

 will not be possible to classify on a natural plan until exact information has 

 been obtained and recorded in terms of cell life, of structural features, such 

 as for example pigmentation of certain areas, the upbuilding of unicellular 

 or multicellular hairs of definite structure, or the development of thickening 

 zones, etc. When such data have been accumulated *Mt will be possible to 

 classify plants on a natural plan, instead of, as now, by selecting one or two 

 Jjoints of resemblance — not necessarily of morphological contact — as a 

 taxonomic basis." — W. J. G, Land. 



In A PRELIMINARY paper concerning a series of experiments now in 

 progress at Harvard Botanic Garden. A. B. Plowman =5 gives some interesting 

 results. Both soil and water cultures of seedlings subjected to as near 

 normal conditions of temperature, light, and moisture as possible, were 

 treated with both static and kinetic charges, through a range of potential from 

 0-5 to 500 volts. Seeds near the anode were killed by a current of 0.003 

 amperes or more, while those near the cathode were little affected or even 

 stimulated. In both water and soil cultures of seedlings the same facts were 

 established. In case the current was allowed to act for a sufficient length of 

 time the ill effects wxre produced at all points between the electrodes, but 

 slower in the soil cultures. With a current of 0.08 amperes or less the seed- 

 lings near the cathode showed an increase in the rate of growth. A provi- 

 sional theory based on the disputed ionic theory is offered in explanation. 

 From certain facts established by experiment the conclusion is made that 

 negative charges stimulate and positive charges paralyze the protoplasm of 

 young seedlings. For example, a positive charge of 500 volts killed lupine 

 seedlings, while a negative charge of similar potential actually stimulated the 

 plants ; in water cultures subjected to a weak current of electricity the root- 

 tips turn towards the anode. The explanation for the latter is that the side 

 of the root tow^ard the anode is retarded in its growth by the positive ions, 

 while the opposite side is stimulated by the bombardment of the negative 



''^ Certain relations of plant growth to the ionization of the soil- Am. Jour. Sci^ 

 14 : 129-132. 1902. 



