Denniston—Growth and Organization of the Starch Grain. 665 
Various theories were held by the earlier writers as to the 
nature and manner of origin of the chloroplasts or chlorophyl- 
bearing bodies of the cell. Mulder believed that they form 
from starch grains. Von Mohl thought that they have their 
origin in the cytoplasm. Schimper (34, p. 6) first developed 
the conception that the chloroplasts are permanent cell organs 
and arise only by the division of pre-existing similar bodies. 
He studied especially Hyacinthus, Daphne and Torenia, three 
plants widely separated systematically, and found chromato- 
phores in the embryo-sac and egg cell of each. He also found 
chromatophores in the egg cells of the moss Atrichum and of 
the liverwort Anthoceros. On these observations he bases his 
doctrine that the chloroplasts are permanent cell organs and 
never arise de novo from the cytoplasm. Schimper also devel¬ 
oped the doctrine that chlorophyl bodies, leucoplasts and chro¬ 
moplasts are all homologous structures and proposed the term 
“plastid” to include them all (34, p. 30). He also believed that 
the leucoplasts and chloroplasts are capable of further meta¬ 
morphoses into other sorts of plastids, but that the chromoplasts 
are fixed, as a rule, although he claims to have found the red 
and yellow chromoplasts in the carrot becoming green on expo¬ 
sure to light. 
Schmitz (37) described the presence of chloroplasts in both 
the egg cells and spores of the Algae and agrees with Schimper 
that they are permanent cell structures for these plants. Von 
Mohl, in 1837, discovered that the chlorophyl grains can be 
separated into two substances, a green material soluble in al¬ 
cohol and ether, and a colorless proteid which determines the 
form of the grain. Sprengel and Meyen believed the chlo¬ 
rophyl grains to be little vesicles. Hageli was a supporter of 
the latter theory and thought that he could distinguish in the 
chloroplast a whitish membrane with green contents. 
In more recent times the vesicular theory has had but few 
supporters, and Von Mohl’s theory as elaborated by S'achs is 
the one generally accented. According to this latter view, the 
chlorophyl grain is composed of a ground mass of colloidal 
consistency which in its chemical composition is probably a 
proteid. In this the green substance is imbedded. 
