President's Address. 31^^' 



change in colour is the only immediate effect apparent ; the whole 

 tissue, like the chlorophyll-corpuscles in the cells, acquires a yellow- 

 green, gold-yellow, or brownish tint. Xo decomposition of the 

 green colouring matter has taken place, nor is it dissolved by the 

 acid, and the chlorophyll-corpuscles are unchanged in form and 

 structure, But after a few hours there appear in the substance of, 

 but chiefly near the periphery of the chlorophyll-corpuscles, dark 

 reddish-brown or rust-coloured, soft, greasy masses, hardly of the 

 nature of drops, beiug of irregular form, and sometimes showing a 

 firmer limiting layer or peUicle. These, which are distinguished by 

 their larger size, irregular form, colour, and denser consistence, from 

 the drops exuded after warming with water, appear invariably in all 

 plants, whatever their position in the vegetable kingdom, and what- 

 ever be their habitat, whether land, fresh or sea water, that contain 

 chlorophyll, be it attached to isolated chlorophyll- corpuscles or to 

 variously shaped masses, and they appear equally in those which 

 contain starch or oil in their corpuscles and in those which have no 

 starch. The following are some of the plants in which these have 

 beea specially observed : — Amongst Algce, species of Ulothrix^ 

 DrapanmJdia, Chcetophora, Aphanochcete, CokocJicete, Mesocarpus, 

 Spirogym, Cladopfiora, (Edogonium, Bidbochcete, Glosterium, Mias- 

 terias, Pediastn.um, and in Enteromorplieoe, Cladophorece, from the 

 German Ocearu Amongst mosses, ia the protonemata, leaves and 

 stems of Mniiim, Hyprnirn, Fontinalis, and Sphagnum. Amongst 

 vascular cryptogams, in pro-embryos oi Fte)-is,BIechnum,ani Gymno- 

 gramme, and in leaves of species of Selaginellece. Lastly, amongst 

 Phcenogams, in leaf tissues of Taxus, Zvstera, VaUimeria, Elodea, 

 CtratophyUum, Heliconia farinosa, Tdia, and Ampelopsis. This 

 effect is not observed in plants that are not chlorophyll green, e.g., 

 in Phycochromacece, Diatomaceoi, Phceosporece, Fiicactce, Flondece, 

 and Fungi,- — traces of it only were observed in some stages of then- 

 life history in diatoms, — although the exudation of colour drops 

 after warming in water may be observed. The VaucTieriece are a 

 curious exception, as in them frequently no trace of the action is 

 visible. 



After a short exposure to the acid, in from six to sixty hours, the 

 rust-coloured masses begin to change in appearance. They become 

 angular and spikey, and form on the surface of the corpuscle more or 

 less broad scales or nests, with an indistinct crystalline texture, 

 from which sharp-edged and pointed prolongations develop, or they 

 form cloud-hke precipitates with fiimer embedded pieces. At a 

 later period stiU further changes take place, and these go on equally 

 well if the specimen be left in the acid or removed to pure water. 

 From the irregular masses are developed short, still, stiaight (often 



