126 AGRICULTURE OF MAINE. 



their full capacity. This same arrangement also provides less 

 favorable conditions for the development of scab and it also 

 facilitates the application of protective sprays to the interior 

 portions of the top. 



Starch is of almost universal occurrence in green plants and 

 is an important plant food. That it is manufactured in the 

 green leaves and only in the presence of certain active rays of a 

 beam of sunlight is a fact easily demonstrated by any school 

 boy. While starch is constantly being formed \\hen the sun is 

 shining on a green leaf it is in the form of grains and not in 

 solution. By other agencies it is constantly being converted into 

 closely related soluble substances like sugar and transported to 

 other parts of the plant. There it is either used at once or con- 

 verted into starch again and stored till future needs require it. 

 The potato gives a familiar illustration of this. Here the food 

 material manufactured by the parent plant the season before is 

 stored up in the tuber ready to be used as a source of nourish- 

 ment for the young plant till it has developed a root system of 

 its own and is able to shift for itself. This transformation and 

 removal of manufactured starch goes on throughout the night. 

 Hence the leaf that at the close of a sunny day was gorged with 

 starch begins the new day with a clean slate ready to repeat 

 the process of manufacture. 



The plant manufactures starch from the elements supplied by 

 carbon dioxide and water alone and releases oxygen in the 

 process, which escapes through the breathing pores of the leaves. 

 The albuminous substances which go to make up the living 

 cytoplasm of the cell contain in addition to the chemical ele- 

 ments found in starch, nitrogen, sulj^hur and phosphorus. In 

 the formation of albuminous substances it is generally held 

 that a part of the sitarch is first converted into some other form 

 of carbdiydratc and that this is in some way combined with 

 the other elements mentioned. 



The course of the long distance transport of the elaborated 

 albuminous food substances in passing back down the branches 

 and trunk differs from that of the upward current of crude ma- 

 terials in that it is carried down in the innermost but living por- 

 tions of the bark just inside of and in contact with the cam- 

 bium zone or region of growth. \\'hen we know the path of 



