292 Ewart, The Relations of Chloroplastid and Cytoplasma. 



The waste products evolved by Bacterium Termo when in 

 water are innocuous, but tlie bye products, produced when grown 

 n meat extract, are exceedingly injurious, A moss leaf within 

 a closed cell in Bacterium containing water, if exposed to light, 

 remains living for an indefinite length of time, but. if mounted 

 in neutralized meat extract with Bacteria, it soon dies. The moss 

 leaf is relatively exceedingly resistant (p. 369, 371 A^). The 

 isolated Chlorophyll grain, it is hardly necessary to point out,. 

 is very much more sensitive. 



It may perhaps be as well to mention that it was a consi- 

 derable time before any definite positive results were obtained, 

 when working on this particular point. Had my own researches 

 been concluded, like those of Kny and Kolkwitz, as soon as 

 the first negative results were obtained, I should perhaps have 

 arrived at the same conclusion as they have done. Fortunately, 

 however, the investigation was persevered with, until it was found, 

 that, under appropriate conditions, with certain plants, positive 

 results could be obtained. To make satisfactory preparations 

 needs some raanipulative skill, and the Omission of any one of the 

 necessary precautions causes negative or unsatisfactory results to- 

 be given. It is hardly necessary to emphasize the fact, that in an 

 investigation of this kind a single positive Observation outvalues 

 almost any number of negative ones, especially if the latter are 

 vitiated by errors of experimentation. That isolated Chlorophyll 

 grains might possess a power of assimilation was deraonstrated io 

 several persons working, at the time, in the Botanisches Institut 

 at Leipzig, including Dr. Klemm, Head assistant and 

 Dr. Richards, now Professor of Botany at Columbia College,. 

 New- York. In addition, a formation of minute starch grains in 

 isolated Chlorophyll bodies has, in certain cases, been observed, 

 provided the power of evolving oxygen was retained for a sufficient 

 length of time. In darkness these did not appear, and hence, 

 apparently, they were not formed from the sugar Solution in which 

 the grains lay. 



Kny and Kolkwitz state that experimenting with Spirogyra, 

 by means of plasmolysis, treatment with acids etc., it is impossible 

 to cause any stoppage of the power of assimilation without 

 killing the cytoplasm. Spirogyra was found at an early stage of 

 my own investigations, to be unsuitable for experimentation in 

 this direction and was therefore not used. In this plant, as in 

 many others, the cell is too sensitive to injurious agencies, and 

 possesses only slight, or no, powers of recovery. It is not 

 impossible that the chloroplastids in this plant are more resistant 

 to injurious agencies than the cytoplasm is. To produce definite 

 results more resistant plants must be employed, and the time 

 during which the injurious agency is actiug must be prolonged. 

 This is only possible, when plasmolytic experiments are performed, 

 by accustoming the plants to sugar Solutions of successively 

 increasing strengths. Even with the short periods given by Kny, 

 it is interesting to notice, that, in one case, after only 10 minutes 



