President's Address. 827 



easily, whilst other blue flowers are decolorised with difficulty, or not 

 at all 



1^(6) Of the ground substance of the chlorop]iyll-coi~pusdes audits 

 included substances in intense light. — The chlorophyll-corpuscles 

 serve not only as organs of assimilation, as has hitherto been sup- 

 posed, but also as organs of respiration. This, their double function 

 in gas interchange, is evidenced by the morphological and micro- 

 chemical changes which their ground substance and contained bodies 

 undergo in intense light. Though green organs under the influence 

 of light give ofl" oxygen, yet the chlorophyll-corpuscles, by reason of 

 their structural and chemical characters, fix oxygen in a liigh degree 

 and at once transfer it to the forming products of assimilation. The 

 physiological value of these substances, formed and deposited within 

 the chlorophyll-corpuscles, falls therefore to be considered alter the 

 behaviour in oxygen and in light of the bodies themselves. 



The ground substance of the chlorophyll-corpuscles and masses 

 after insolation resembles in appearance the condition in which it 

 is left after alcohol or other solvent has decolorised and removed 

 the oil from it. It is a colourless skeleton, unchanged in form, 

 and presents the same sponge-like structui-e as residts from the action 

 of solvents, acids, and moist warmth. In Sjjirogyra the marginal 

 projections on the band (so changeable in the living cell) remain ; 

 only sometimes when an excess of heat has operated, or a consider- 

 able time has elapsed before the death of the band, are the projec- 

 tions withdrawn and the band contracted in Avidth, or the margins, 

 still marked by the projections, become re volute. Chemically little 

 can be said. The skeleton shows a protoplasmic character, and 

 takes up iodine and colouring agents more readily than before, pos- 

 sibly on account of its porosity. Insolation, however, produces a 

 change in the nature of the substance, in virtue of which it offers 

 greater resistance to external influences. Such a change is well 

 illustrated by the case of NiteJla cells kiUed by rapid insolation of 

 a limited area, in which the decolorised chlorophyll-corpuscles of the 

 insolated area remain unchanged in form and shape long after the 

 green corpuscles and contents of the non-illuminated portion of the 

 cell are completely disintegrated. The chlorophyll-bands of Sjnro- 

 gyra and the chlorophyll-masses of other plant cells, which, as is 

 known, are extremely sensitive to injurious influences, such as 

 increase of temperature, mechanical irritation, &c., losing their form, 

 contracting, rupturing, or swelling into variously-shaped bodies, 

 behave when decolorised by insolation in the same way as the 

 chlorophyll-corpuscles in XiteUa. The light-killed bands stifi"eu 

 wliile retaining their normal form and configuration. The ground 

 substance of chlorophyll-corpuscles and masses appears thus under 



TRANS. BOX. see. VOL. XIV. Z 



