466 



THE QUARTERLY REVIEW OF BIOLOGY 



the "protoplasmic molecules" of the 

 chloroplasts. Mikosch held that grains 

 of starch could transform themselves into 

 chlorophyll granules and Stohr also noted 

 that the formation of the grains of chloro- 

 phyll was often preceded by the formation 

 of grains of starch. 



Frommann held that the whole plastid 

 was composed of a fundamental network 

 of green threads. It was Pfeffer who 

 first showed that the plastid could not 

 carry on photosynthesis in the absence of 

 the chlorophyll which it normally con- 

 tains. Pringsheim came to the conclu- 

 sion that the ground substance of the 

 chloroplast is a hollow sphere possessing a 

 spongy structure and that it holds the 

 green coloring matter in its meshes. He 

 thought that the green pigment was only 

 mechanically associated with the frame- 

 work. Schimper recognized that the 

 plasma structures do not necessarily arise 

 from the undifferentiated plasma but prob- 

 ably arise as do nuclei by the division of 

 preexisting structures of the same sort. 

 Chodat agreed in general with Pringsheim 

 and Tschirch as to the spongy structure of 

 the chloroplast. Bredow found that the 

 ground substance of the chlorophyll bodies 

 is not composed of fibrils. Kerner held 

 that the groundwork of the chlorophyll 

 granules differs but little in structure and 

 composition from the surrounding proto- 

 plasm. Wagner observed in certain cases 

 a distinct fibrillar arrangement of the 

 chlorophyll within the chloroplast. He 

 was inclined to the view that the chloro- 

 phyll corpuscle consists of a ground sub- 

 stance in the form of a delicate alveolar 

 structure, in which the chlorophyll is 

 more or less diffused. 



Mereschkowsky believed that the 

 chromatophores are not organs which 

 have been differentiated from cell plasma 

 but foreign bodies or organisms enclosed 

 in the colorless plasma of the cell and 



existing symbiotically with it. A plant 

 cell is nothing more than an animal cell 

 with Cyanophyceae contained in it. 

 Plants thus have been derived from ani- 

 mals. Others are of the opinion that 

 chloroplasts have been formed from mito- 

 chondria; Meyer, however, is opposed to 

 this conclusion. Liebaldt accepted the 

 hypothesis that the green lipoid phase 

 and the hydroid phase exist as fine emul- 

 soids. 



This brief summary shows us that our 

 concept of the chloroplast is not at all a 

 definite one. There seem to be about as 

 many concepts of the chloroplast as there 

 are workers. Just what general idea is 

 most prevalent regarding the chloroplast 

 would be very difficult to state. Let us 

 now take a closer view of the oil which is 

 present in the chloroplasts. 



Sachs observed that sometimes drops of I 

 oil form in the interior of the chloroplast. , 



Briosi was the first to recognize oil ! 

 droplets in the chloroplast as perfectly I 

 normal inclusions and did not consider the : 

 oil as a result of a pathological condition. J 

 He showed that in several species of I 

 Strelifzia and Musa no starch occurs. Oil 

 droplets instead of starch grains arise in 

 the chloroplasts of these plants and this I 

 oil exists in finely divided particles be- 

 tween the "protoplasmic molecules" of; 

 the chloroplasts. In this connection it is 

 interesting to note that Pringsheim 

 thought that the green pigment is only \ 

 mechanically associated with the frame- 

 work. 



Bredow found that oil droplets were : 

 present now and then in the meshes of the : 

 chloroplasts. Liebaldt considered that 

 the chloroplasts of the higher plants 

 consisted of two phases, a hydroid phase 

 and a green one of lipoid character. The 

 chloroplasts appeared to be homogene- 

 ously green or finely granular. Because 

 of the fact that in most cases no definite 



