Carter . — Studies on the Chloroplasts of Desmids. IV. 317 
In those species in which the points at which pyrenoids may occur are 
fixed the young semi-cell is provided with a corresponding number of pyre- 
noids by the budding of those already existing in the old semi-cell. Where 
the pyrenoids are indefinite in number and scattered, a number of these 
enter the new semi-cell together with the budding chromatophore. 
A striking feature of the ingrowth of the chloroplast in many species is 
the rapidity with which the cell-wall of the young semi-cell is completely 
mantled by the chloroplast, often at the expense of the more central parts 
of the semi-cell. This phenomenon is responsible for the formation of 
parietal chloroplasts in isolated specimens of species which normally possess 
axile ones, and probably also for their original production in species in 
which they have been permanently acquired. 
In conclusion I have to acknowledge the invaluable help and advice 
which I received throughout the whole of this investigation from the late 
Professor G. S. West, and also my indebtedness to him for providing much 
of the material. My thanks are also due to the Birmingham Natural 
History and Philosophical Society for a grant from their Endowment of 
Research Fund to help in the cost of producing the plates illustrating this 
work, and also to the Royal Society for a further grant for the same 
purpose. 
The Botanical Laboratory, 
University of Birmingham. 
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