1030 SUMMARY OF CURRENT RESEARCHES RELATING TO 



of the elements phosphorus, potassium, magnesium, calcium, sul- 

 phur, iron, and chlorine to be regarded in this light cannot, Mr. 

 T. Jamieson thinks, be considered conclusive. 



A little consideration shows that the two elements iron and chlorine 

 have but little claim to be considered as essential to the food of 

 plants ; and the experiments, of which an account is given, were made 

 by the author with the view of vindicating the right of the five re- 

 maining elements to be so considered. These investigations were 

 conducted at an experimental station in Sussex and also at one in 

 Aberdeenshire, the nature of the soil in both cases being specially 

 favourable. The method adopted consisted in observing the effect on 

 plants grown in similar soil and under similar conditions when sup- 

 plied with manures containing all these elements, and comparing the 

 results with those obtained when one or other of these elements was 

 withheld. The experiments seem to provide proof that sulphur must 

 be discarded from the list of essentials, while some doubt is thrown 

 on even lime and magnesia. At the same time striking confirmation 

 is afforded of the essential characters of both phosphorus and 

 potassium. 



Digestion of Proteids in Plants.* — Of proteolytic ferments oc- 

 curring in plants two kinds have been described — one acting like 

 animal pepsin, and occurring in carnivorous plants, in the seeds of 

 vetches, hemp, flax, barley, and malt, and the fruit of the fig, Ficus 

 carica; the other acting like animal trypsin (pancreatin), and occurring 

 in the juice of the green fruit of Carica Papaya (the papaw tree). The 

 use of these ferments in the plant economy has also been surmised by 

 testing their action on animal proteids, from which they form pep- 

 tones. It is a question whether they form peptones from the proteid 

 occurring in the individual, and from two considerations. It is 

 doubtful whether a true peptone exists in plants, i.e. a proteid 

 soluble in water, and not precipitated by boiling, nitric acid, or 

 acetic acid and potassic ferrocyanide. Vines concludes that the body 

 called vegetable peptone is hemialbumose (Meissner's a-peptone). It 

 is also evident that the action of these ferments on the proteids will 

 be slow in comparison to the action of animal proteolytic ferments ; 

 thus there might appear the proteids intermediate between albumen 

 and peptone, which Kiihne and Chittenden call alhumoses. 



These questions Dr. S. Martin attempted to settle in the case of 

 the papaw juice. He first of all extracted the proteids, which con- 

 sisted of a globulin, corresponding to animal paraglobulin ; two 

 albumoses, which he proposes to call a- and (i-phytalhumose. The /3 

 form is precipitated ; the a form is not thrown down by boiling ; a 

 vegetable albumen corresponding to egg-albumen. The effect of pure 

 papain (the proteolytic ferment of the papaw juice) was tested on 

 each of these bodies, but from none of them was a true peptone 

 formed ; only a body corresponding to Meissner's &-peptone. The 

 very slow proteolysis explains the limitation of the formation of the 

 final products of proteid change. Leucin and tvroin were formed. 



* Nature, sxxii. (1885) p. 563. (Paper read before the British Associaticn.) 



