PRINGSHEIM S RESEARCHES ON CHLOROPHYLL. 79 



The effect of treating green tissues with dilute acids is some- 

 what different, and has led to the discovery of a universally 

 present constituent of the chlorophyll-corpuscles, — hypo- 

 chlorin. Hydrochloric acid, in the proportion of 1 vol. to 4 

 vols, of water, is the most favourable for the detection of this 

 substance. But others may be used, e.g. sulphuric acid, 1 

 vol. to 20 — 40 vols, of water ; glacial acetic acid, 1 vol. to 

 2 — 4 vols, of water; picric acid, 1 vol. to 3 — 6 vols, of water; 

 these, however, require much care in application, and are less 

 certain in their effect than hydrochloric acid, which has been 

 chiefly used in these investigations. Grlacial acetic acid, 1 

 vol. to 2 vols, of water, is specially favourable for bringing out 

 the perforated wall-structure of the chlorophyll-corpuscles. 



In specimens preserved for some years in Hantz's fluid, in 

 dilute glycerine, and in chloride of calcium, hypochlorin was 

 observed to have exuded from some chlorophyll-corpuscles. 



If a green tissue be treated with dilute hydrochloric acid, 

 a sudden 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. No decomposition of the green colouring matter has 

 taken place, nor is it dissolved by the acid, and the chloro- 

 phyll-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, being of irregular form, and 

 sometimes showing a firmer limiting layer (fig. 4) or pellicle. 

 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, 

 Avhatever 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 chloro- 

 phyll-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 fol- 

 lowing are some of the plants in which these have been 

 specially observed : — Amongst Alga, species of Ulothrix, 

 tiraparnaldia, Chcetophora, Aphanochcete , Coleochcete, Meso- 

 carpus, Spirogyra, Cladophora, QHdogonium, Bulbochate, 

 Closterium, Micrasterias , Pediastrium, and in Enteromor- 

 plie(B, Cladophoreee, from the German Ocean. Amongst 

 mosses, in the protonemata, leaves and stems of Milium, 

 Hypnum, Fontinalis, and Sphagnum. Amongst vascular 

 cryptogams, in pro-embryos of Pieris, Blechnum, and 



