Ewart, The Relations of Cbloroplastid and Cytoplasma. 293 



immersal in 30°/o sugar Solution, the power of assimilation did 

 not return until after a period of half an hour, during which time 

 the chloroplastids were unable to assimilate , i. e. were in a 

 condition of assimilatory inhibition, although the cell remained 

 living and finally recovered, This Observation coincides fairly 

 well with those made bj myself on Elodea (p. 435. A^), the reco- 

 very here taking place, owing to the longer time of immersal, not 

 during the V» hour in 20*^/0, partly during the succeeding Va hour 

 in lO^'o? 'ind completely when returned to water. 



The inhibition of the power of assimilation, in Chlorophyll 

 bodies contained in a living cell, which may persist for a time, 

 after the injurious agency has been removed, is due to a patho- 

 logical condition, which may be induced in the chloroplastids of 

 many plants by the prolonged Operation of almost any injurious 

 agency of sufficient intensity to depress the functional activity of 

 the chlorophyllous cells to the lowest possible ebb, consistent 

 with the preservation of vitality. From this pathological condition 

 recovery may or may not be possible. In the latter case the 

 cell is converted inlo a non-chloroph^dlous ooe, and yet has been 

 shewn to be capable of remaining living for a week or more 

 (p. 376, 390, 391, 439. A^ p. 574. A^). In some plants it has 

 been found almost impossible to inhibit the power of assimilation 

 without at the same time killing the cytoplasm. In other 

 plants, the Operation of certain injurious agencies only, may cause 

 an after inhibition of the assimilatory power of the chloro- 

 plastids , while all other agencies , however applied , cause the 

 death of the cytoplpsm before the cbloroplastid is markedly 

 affected. 



The results of experiments, which are at present in progress, 

 seem to shew that the chloroplastids of mosses and the gonidia 

 of Lichens, exposed to light in an atmosphere deprived of CO2, 

 retain the power of assimilation as long as the cells remain 

 living, although as has been previously shown (pp. 567 — 573. 

 A^), under such conditions, the chloroplastids of many higher 

 plants speedily lose the power of C02-assimilation, though the 

 cytoplasm of the cells in which they lie, is at first living and 

 normal, and may remain so, if the power of recovery has not 

 been lost. 



The application of moist heat alone, is, as a general rule, 

 followed, if the cell remain living, by a rapid or imraediate 

 return of the power of CO^-assimilation (p. 386. A^), but here 

 also, especially if combined with a certain amount of asphyiation 

 (p. 387 and 388. A^) an inhibition of the power of C02-assimilation 

 may be produced in living cells. 



It is needless to recapitulate turther. Füll details will be 

 found in the previous publications, in which Kny and Kolk- 

 witz 's observations on the rapid return of the power jCof 

 assimilation to living air dried mosses, and on the presence of a 

 power of assimilation after rotation had been caused to stop, have 

 already been given (pp. 385, 395. A^ p. 152. B'). 



