President's Address. 317 



characteristic exudations have been developed, be treated with 

 dilute hypochloric acid, no hypochlorin masses are formed, neither 

 on the coloured drops nor on the ground-substance of the chloro- 

 phyll-corpuscle, provided that the duration of warming and the 

 temperature have been sufficient for the tissue and species examined 

 Usually the only visible effect is a slight change to a browner tint 

 of the coloured drops. The time and temperature limits vary con- 

 siderably with the species. Thus, for Mesocarpus scalaris, which is 

 very rich in hypochlorin, five minutes' exposure to a temperature of 

 42°-43° C. suffices ; Cladojjlwra requires five to fifteen minutes at 

 50° C. ; in Spirogyra, Ulothricliece, Coleochcetece, CEdogo7iiece, and 

 their allies, a temperature of 45°-50° destroys the reaction. For 

 plants with isolated chlorophyll-corpuscles, such as Chara and 

 Nitella, and soft-leaved plants as Elodea, Ccdlitriche, &c., a quarter 

 to half an hour in water of 50° is enough. Fontincdis also takes 

 fifteen minutes at 50° C. In Mnium, fern embryos, Selaginella, 

 and in Vallisneria, a longer time at 50° C. is required, or the tem- 

 perature must be raised to 60°-80° C. Boiling or steaming brings 

 it about more rapidly. Fifteen minutes steaming is enough, as a 

 rule, though at times half an hour or an hour is wanted. It would 

 appear that in all these cases the hypochlorin is destroyed by heat, 

 and vanishes without damage to the colouring matter or destruction 

 of the chlorophyll-corpuscle or mass itself. 



Other hurtful influences, which only to a slight extent change 

 the normal character of the cell-content, destroy the hypochlorin 

 without there being any visible change in the chlorophyll-corpuscle 

 itself. Cells in such an abnormal or unhealthy state occur fre- 

 quently in cultivated specimens of Spirogyra or of Nitella. They 

 can easily be produced artificially if the conditions of life are made 

 unfavourable. If a cell of Spirogyra be injured mechanically, or if 

 the conditions for its existence are not suitable, the first sign of un- 

 healthiness is seen in the chlorophyll-bands, which lose their out- 

 line, contract, and if the conditions be continued disintegrate to 

 formless particles. Such signs are very frequently indication of a 

 faulty nutrition only. The colour of the bands is not in the least 

 affected, and the amylum-bodies and oil-drops remain undestroyed. 

 Many cells in a filament may be quite healthy, and others may show 

 all stages of commencing sickness. On treating with hydrochloric 

 acid, the healthy cells alone show hypochlorin, none is found in the 

 unhealthy cells, or only a slight trace when the diseased state is not 

 very pronounced. It is possible that some of the cases already re- 

 ferred to where one or more cells in the midst of a tissue rich in 

 hypochlorin show no trace of this substance, and in which the hypo- 

 chlorin was supposed to have been completely used up in the nutri- 



