STARCH FORMATION IN ZYGNEMA 
CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 238 
HELEN Bovurquin 
(WITH PLATE XXVII) 
Between 1880 and 1895 much literature on the subject of starch 
formation appeared. At that time certain problems in regard to 
the origin of starch grains in algae arose which have not yet been 
settled. The present investigation of Zygnema was undertaken 
because its chromatophore appears to be typical of many algae, 
and it is so large that the possibility of error in cytological work 
should be minimized. 
History 
The most important investigations on starch formation were 
made by MEYER (3, 4). One of his conclusions is that starch 
is always formed by the plastid by secretion. Although he con- 
fined most of his attention to angiosperms, he believed this to be 
equally true for algae (4). He concludes that the pyrenoid is 
reserve protein material which is formed by the plastid and is 
used by the cell after its supply of starch has been exhausted. In 
his opinion it is homologous with the protein crystals formed in 
the plastids of many of the lower monocotyledons, which are like- 
wise utilized after all the starch grains have disappeared. The 
plastid itself he sees as a colorless or slightly yellowish honeycombed 
structure (“‘vakuolig-porése’’), which contains chlorophyll in the 
form of granules. Other investigators agree that the pyrenoid 
is implicated in some way in the formation of starch in algae. 
Scumitz (7) finds a specific pyrenoid substance which is laid 
down locally in the substance of the plastid in such quantities that 
the mass appears as a structure more or less sharply differentiated 
from the plastid. Although formed by the plastid, this pyrenoid 
substance is living and takes an active part in starch formation. 
He adds that in many cases the plastid forms starch without the 
intervention of the pyrenoid, and that pyrenoids often appear in 
Botanical Gazette, vol. 64] [426 
