Miscellaneous. 



64 



[July, 1909. 



degree that it will harden when cooled. 

 Then spread ont the paste on a marble 

 slab and cut into any size and shape you 

 like. During the process of boiling 

 some flavouring essence like vanilla or 

 cinnamom might be added. The pro- 

 portion might be 2 lb. sugar (for the 

 syrup) to 1 pound of the fruit pulp. The 

 possibility of the extended usefulness, 

 especially from a medical point of view, 

 of this confection of slime-apple (the 

 virtues of which are too well known), 

 like the confections of figs and tamarind 

 now in use, are I think considerable- 

 C. DRIEBERG, 



Secretary, 0. A. S. 



THE BLOOD OF PLANTS. 



(From the Gardeners' Chronicle, XLV., 

 1169, May, 1909.) 

 It has long been known that the blood 

 of animals contains substances— respira- 

 tory pigments— which act as carriers of 

 oxygen ; that is, which are capable of 

 uniting with oxygen and of yielding it 

 up to the tissues of the body. Such 

 respiratory pigments are contained, for 

 example, in mammalian blood, and to 

 them that fluid owes its characteristic 

 colour. The change of colour which 

 blood undergoes in passing from the 

 arterial to the venous state is due to the 

 change in colour of the respiratory 

 pigment. When united with oxygen it 

 is bright red, and when deprived of 

 oxygen it is of a darker colour. 



Again, it is well known that in the 

 process of respiration, both in plants 

 and animals, the energy which this 

 process releases and puts at the disposal 

 of the organism is in part due to oxida- 

 tions. The raw materials of respiration 

 are complex organic compounds— sugar 

 and also nitrogen-containing bodies : 

 the final " waste" products of the process 

 are fully oxidised substances, such as 

 carbon-dioxide, water and the like. 



It has always been a puzzle to physio- 

 logists to understand by what chemical 

 course of events the respired substances 

 are oxidised in the cells of the plant or 

 animal. 



It has been evident for some time that 

 respiration is not a simple oxidation 

 process, for if it were, then increasing 

 the supply of oxygen should result in 

 increased respiration. This is not the 

 case with plants, for the amount of 

 oxygen in the air supplied to the plant 

 may be varied within extraordinarily 

 wide limits without increasing the rate 

 of respiration. 



That certain processes go on in the 

 plant preliminary to the oxidative pro- 



cesses which constitute the last stage of 

 respiration is evident from the study of 

 fermentation by yeast. 



Yeast is a fungus which, as is known 

 to all, converts certain sugars into 

 alcohol and carbon dioxide. Yeast 

 (Saccharomyces cereviseai) is remark- 

 able, inasmuch as it may live in the 

 presence or in the complete absence of 

 oxygen ; or, in other words, it can live 

 eerobically or anserobically. 



When oxygen is present yeast, besides 

 fermenting a certain amount of sugar to 

 alcohol, converts some sugar into carbon 

 dioxide and water, that is, it sets up 

 fermentation and also respires like an 

 ordinary plant. When oxygen is absent 

 yeast obtains its supplies of energy 

 solely by breaking sugar molecules into 

 alcohol and carbon dioxide. 



Yeast, as an serobe, derives the major 

 part of its energy thus : — 



6 Hi2 d + 6 02 = 6 C02 + 6H 2 

 as an auajrobe, thus : — 



C0H12 0e=2 O2H5H + 2 CO2 

 and since the energy obtainable from 

 a given weight of fermentable sugar is 

 greater when the oxidation is complete, 

 as in the former case, than when the 

 sugar molecule is splilt into an unoxi- 

 dised part (alcohol) and an oxidised part 

 (carbon-dioxide), it follows that, to get 

 the energy necessary for its routine 

 work of livine, yeast as an anrarobe 

 must decompose considerably more 

 sugar than when it is living as an 

 aerobe. This is confirmed by the ex- 

 perience of brewers, who limit the 

 amount of oxygen available for the 

 yeast during alcoholic fermentation. 

 Till recently the facts of alcoholic fer- 

 mentation were regarded rather as 

 curious than significant. Two sets of 

 observations have forced them into 

 prominence as throwing light on the 

 chemistry of respiration. The first set 

 of observations indicates that alcoholic 

 fermentation is not confined to yeast and 

 various other micro-organisms, but may 

 be demonstiated to occur among the 

 higher plants. That this is so, anyone 

 may determine very readily by keeping 

 Bean seeds under water for a few days, 

 and then rubbing the seeds between 

 the fingers, when a distinct smell of 

 alcohol is to be recognised. Experi- 

 ments on the behaviour of the higher 

 plants when deprived of oxygen have 

 led to the conclusion that in these 

 circumstances, though no oxygen is 

 absorbed, carbon-dioxide continues for 

 some time to be evolved ; and, as we have 

 just seen, alcohol is also produced. This 

 process of respiration without oxygen is 

 called generally intra-molecular respira- 

 tion. It agrees in the most exact manner 

 with the alcoholic fermentation of sugar 



