THE ALUMNI JOURNAL 25 



is exposed to the light. The chlorophyll bodies, called chloroplasts, 

 consist of one or probably two albumenoid substances of a spongy 

 texture, in the meshes of which the coloring matters together with 

 other substances (oil) are embedded. The body is surrounded by 

 a very fine plasma membrane. Stroma as well as membrane are soft 

 and plastic ; the granules can therefore change their shape readily. 

 A cell densely filled with granules — sometimes we find fifty to sixty 

 granules in one cell — will show them in triangular, quatrangular or 

 polyangular form. The membrane, however, prevents the granules 

 from forming one mass. Upon the death of the cell, the membrane 

 disintegrates and granule-body and contents form one shapeless mass. 

 At the same time, the bright green color is changed to a brown, due 

 to the presence of acid cell juices which can and do now attack the 

 coloring matter. For this reason, our dried drugs, especially those 

 which have not been dried carefully, present a brownish-green ap- 

 pearance. 



Besides the coloring matters, we find certain colorless bodies and 

 protein masses in the chloroplast. The chlorophyll is looked upon as 

 the substance which assimilates the CO, ; the colorless bodies probably 

 assist in the storing of the starch formed and in changing it into 

 soluble diastase. Under the influence of light, CO, and HjO are 

 changed into starch and this is stored. When the starch production 

 rests (at night) the starch is changed into diastase. The function 

 of these chloroplasts is of greatest importance for the life of the 

 plant as well as for our own. They convert the energy of the sun 

 into vital energy. CO, and H2O are formed into starch and other 

 substances which serve as food for plant and animal. 



In plant parts not exposed to light, so called chromoplasts or bodies 

 containing a yellow coloring matter take the place of chloroplasts. 

 These chromoplasts, however, occur also in plant parts exposed to 

 light, such as certain flowers, and are often formed from the chloro- 

 plasts. We have evidence of this in the change of color when apples 

 or oranges ripen. 



Starch is the first visible product of the chromoplast's photosyn- 

 thesis, although simpler intermediate compounds are doubtless first 

 formed. This starch is converted into soluble form at night and 

 carried, in solution, into plant parts requiring nourishment. 



Several conditions are absolutely necessary for the formation and 

 function of chlorophyll. First of all and most important is light. 



