318 President' fi Address. 



tive process, are instances of disease. The cells, though not visibly 

 so, may be really in an abnormal condition, which has resulted in 

 and is made known by the loss of their hypochlorin. 



Associated, then, with the colouring matter, hypochlorin is a 

 substance universally present under normal conditions in chloro- 

 phyll-corpuscles, whatever their shape. These having the structural 

 character of a hollow sponge or network, their meshes are permeated 

 by the hypochlorin and the oily vehicle with the colouring matter, 

 which can, by the methods mentioned, be readily extracted. In 

 the interior, too, of these hollow perforate chlorophyll-corpuscles, 

 the secondary deposit of starch and such like formative material 

 takes place. The whole organisation of the chorophyll-corpuscles 

 is thus admirably suited for the performance of their function, and 

 they are peculiarly fitted for absorbing and condensing gases. 



Next may be noticed his observations on — 



Efect of Light. — Paralysis and Death from Light. 



The time which elapses before visible effects appear in a cell 

 exposed to intense light varies according to the specific energy of 

 the cell. In most plants, and without exception in green plants, 

 a few minutes suffice for their appearance, and the extent of the 

 action can be regulated so that transformations may be brought 

 about in the ceU-coatent without injury to the life of the cell, or 

 paralysis and death of the cell may be produced. Some cells, how- 

 ever, especially non-green ones, for example, colourless swarm-spores 

 which are very sensitive to heat are but slightly affected, and may 

 remain for half an hour or more exposed to the concentrated white 

 light without injury, — an important fact, as showing that a cell is 

 not of necessity killed or injured when exposed in water to the heat 

 which is generated in the focus of a large lens. 



For investigation of the effect of intense light on green tissues, 

 Algoi, Gliaraceoi, moss leaves, hairs and soft leaf-tissues of Fluviales, 

 are favourable subjects, as in them the effect is generally apparent 

 in from two to six minutes. 



If species of Spirogyra, such as nana, jugalis, qutnina, or Weberi, 

 be exposed to intense light, the effect immediately observed is 

 complete disappearance of colour from the chlorophyll-bands. The 

 ground substance remains unchanged in form and disposition, and 

 the marginal projections and amylum bodies persist. The band 

 appears as if acted upon by alcohol, and the decolorisation is 

 limited to the insolated area, though at times there may be a slight 

 halo. It is possible to restrict the action of the light to one coil of 

 the chlorophyll-band or to a portion of it, or, if a plant be employed 



