104 pringsheim's researches on chlorophyll. 



Hypochlorin, on the other hand, disappears from cells 

 exposed to intense light, and no trace of it remains. If a 

 filament of Q^dogonium, Spirogyra, Cladophora, or Mesocarpus 

 he exposed to intense light, there is decolorisation of the in- 

 solated area; the cells of the rest of the filament are un- 

 changed. If now dilute hydrochloric acid he added hypo- 

 chlorin appears in the usual way, after from six to twenty 

 four hours, in the non-exposed areas, but none is seen over 

 the insolated portion. If, in Spirogyra^ insolation is inter- 

 rupted before the chlorophyll colouring matter of the hands 

 is dissipated, no hypochlorin is found on the slightly or half- 

 decolorised bands, though it is present on the non-insolated 

 bands. Five to six minutes of insolation suffice to decolorise 

 the bands of Spirogyra jugalis ; under the same conditions 

 two to three minutes are enough for the destruction of 

 the hypochlorin. ^A here there are isolated chlorophyll-cor- 

 puscles the same is observed, e. g. if a portion of a cell of 

 Nitella be exposed (fig. 25). In this plant, however, it some- 

 times happens that no hypochlorin shows on the green chlo- 

 rophyll-corpuscles of the non-insolated portion of the cell. 

 The light effect in this case, it would appear, has spread 

 beyond the immediately exposed area, and this may be ex- 

 plained by the fact that hypochlorin is one of the most easily 

 affected bodies in the cell. Small increments of temperature, 

 mechanical stimuli, spontaneous disease, as already shown are, 

 even when the chlorophyll colouring matter is intact, able to 

 destroy it in the cell. From these facts we may conclude that 

 the disappearance of hypochlorin is the earliest indication of 

 a hurtful influence affecting the plant cell, and its destruction 

 results in intense light earlier than does the destruction of 

 the chlorophyll colouring matter. 



3. Protoplasm of the cell and turgescence as affected hy 

 intense light. — The turgescence of cells is diminished by ex- 

 posure to intense light. In large-celled Alg(£ this is shown 

 by the vertical division wall between insolated and non-inso- 

 lated cells becoming curved into the former (fig. 18, between 

 d and e). The tension of the insolated cell is decreased rela- 

 tively to the non-insolated by the greater permeability (as 

 shown by its behaviour to coloured solutions) for cell-sap of its 

 protoplasmic utricle. If a filament o\ Spirogyi'a, some cells 

 of which have been insolated, be laid in a watery solution of 

 vesicles are at first broken, the cell contents collapse, and the cbloropbyll- 

 plate contracts, but the colour of the plate remains unchanged (fig. 21). 

 In blue light in the same or in shorter time the chlorophyll-plate loses its 

 colour and contracts, the cell contents collapse, but the tannin-vesicles 

 remain I'or some time intact, and only at a later period coalesce when the 

 insolation has entirely ceased (fig. 20). 



