July, 1909.] 



65 



Miscellaneouos. 



by yeast, and, indeed, !only takes place 

 in plants which contain sugar in their 

 tissues. The second set of observations 

 bearing on the chemistry of respiration 

 are due to Buchner, who has succeeded in 

 isolating from the living yeast-cell a defi- 

 nite substance which he terms zymase, 

 and which, like the living yeast-cell 

 itself, has the power of decomposing 

 sugar into alcohol and carbon-dioxide. 



From these results it would appear pro- 

 bable that in yeast, living in oxygen, res- 

 piration takes place in a series of 

 stages, of which the first is the disrup- 

 tion by zymase and similar agents of 

 complex, organic substances such as 

 sugar (and also nitrogen-containing 

 bodies), and the second the oxidation of 

 the alcohol and other substances pro- 

 duced by this disruptive action. If this 

 is the probable course of events in the 

 respiration of yeast, it is also, for the 

 reasons already given, the probable 

 course of events in the respiration of 

 all plants. 



In this scheme the respiratory pig- 

 ments find a definite place. These pig- 

 ments consist of readily oxidisable 

 bodies, and, under the influence of 

 special agents of oxidation called 

 oxidases and peroxidases, take up oxy- 

 gen. They act as temporary storers of 

 oxygen. The oxygen, which they hold 

 but loosely, is taken from them and 

 induced to combine with the products of 

 the disruptive process described above, 

 with the consequent production of fully- 

 oxidised substances — the so-called pro- 

 ducts of respiration — such as carbon- 

 dioxide and water. A respiratory 

 pigment may have different colours 

 according as it is in the oxidised or the 

 reduced state ; thus indigo is blue in the 

 former, but colourless in the latter con- 

 dition. Various fungi, such as species 

 of Boletus turn blue when broken and 

 exposed to the air owing to the taking 

 up of oxygen by the respiratory pigment. 

 Many of the common colour changes 

 in vegetables, as, for example, ■ the 

 browning of Apples may be the visible 

 sign of a similar oxidative process where- 

 by a respiratory pigment is converted 

 from its reduced, colourless state to its 

 oxidised, coloured condition ; the oxygen 

 so taken up being destined for respir- 

 atory purposes. Inasmuch as bodies, 

 having these peculiar relations to 

 oxygen and exhibiting marked colour 

 characteristics when oxidised, exist in 

 the sap of the most varied kinds of 

 plants, it has been suggested by Palla- 

 din, to whom the most recent investi- 

 gations are due, that the cell-sap of 

 plants, because it contains these respi- 

 ratory pigments aud also the oxidising 

 agents, is to be regarded as fulfilling the 

 same respiratory functions as the blood 

 of animals. 

 



Looking at matters from the stand- 

 point of the plant, the problem which 

 it solves by respiration is how to obtain 

 the energy for doing its work. The 

 complex substances which it manufac- 

 tures contain potentially great stores of 

 energy. All that is required is that these 

 substances should be oxidised. At the 

 low temperature at which plants work 

 this cannot be done directly. It is done 

 indriectly in two series of operations. 

 First, by special, elastic (decomposing) 

 agents, like zymase, the organic sub- 

 stances are split up into intermediate 

 bodies. In the second set of operations 

 oxygen is brought into close association 

 with the respiratory pigments. In the 

 last place, this store of oxygen is intro- 

 duced to, and caused to combine with, the 

 decomposition-products of the first stage. 

 Thus more or less fully-oxidised pro- 

 ducts are evolved, the fullness of oxi- 

 dation being a measure of the complete- 

 ness with which the potential energy of 

 the original food substance is liberated. 

 Although it cannot yet be described in 

 simple language, easy of apprehension 

 to the layman, the great problem of the 

 mode of origin of the vital energy of 

 organisms, by virtue of which they live 

 and move and have their being, begins 

 to be intelligible. 



SCHOOL GARDENS. 



Their Object, Management, &c. 

 (Teachers' Leaflet No. 1 for 1909,) 

 The following circular, under the three 

 heads (1) Object of School Gardens ; (2) 

 Conditions under which they are work- 

 ed ; (3) Points in the judging of Gardens, 

 is sent for your information and guid- 

 ance :— 



1. — Objects of School Gardens, 

 (a) To brighten the surroundings of 

 the school, and make it what it ought to 

 be, viz., a pleasant resort for the boys 

 and not a bare and unattractive build- 

 ing. 



(6) To lighten the routine of class 

 work by varying it with outdoor work 

 of a recreative nature. 



(o) To exemplify order, form, neatness, 

 and good taste in the laying out of the 

 premises, 



(d) To furnish a field for nature study, 

 i.e., the study of natural objects in their 

 natural surroundings. 



(e) To serve as object lessons in horti- 

 culture, i.e., the cultivation of useful 

 and ornamental plants. 



(/) To give a practical turn to school 

 life, and provide a training in element- 

 ary agricultural science. 



(g) To serve as centres for the disse- 

 mination of seeds and plants and of 

 information concerning them. 



