PLASTIDS AND CHONDRIOSOMES 109 



served that under certain conditions the pyrenoid is closely surrounded 

 by a mass of starch grains, and concluded that it is an organ, or portion of 

 an organ (chromatophore), intimately concerned in the process of starch 

 formation, its action being somewhat similar to that of the amyloplast. 

 The pyrenoid, in fact, has often been likened to a leucoplast imbedded in 

 the chromatophore; Wiesner, for instance, believed the pyrenoid to 

 contain several leucoplast bodies, each of which gave rise to a starch 

 grain. In general, more recent researches have emphasized the close 

 association of the pyrenoid with the starch forming process, although 

 the precise nature of this process remains very much in doubt. Accord- 

 ing to Timberlake (1901) the pyrenoid in Hydrodictyon is differentiated 

 from the cytoplasm and is very active in starch production, segments 

 splitting off from its periphery and forming starch within them. In 

 this way the entire pyrenoid may become a mass of "pyrenoid starch," 

 as distinguished from ordinary, or "stroma starch." McAllister (1913) 

 describes a similar splitting up of the pyrenoid to form several starch 

 grains in Tetraspora. Yamanouchi (1913), however, in his description 

 of a new species of Hydrodictyon, states that some of the chloroplasts 

 give rise to starch while others give rise to pyrenoids, and that the 

 latter have nothing to do with starch formation. 



A similar diversity of opinion exists with respect to the role of the 

 pyrenoid in Zygnema. Chmielewskij (1896), who looked upon the 

 pyrenoid as a permanent cell organ multiplying only by division, held 

 that starch grains arise wholly from the substance of the pyrenoid, 

 plate-like extensions of the latter being present between and in intimate 

 contact with the developing grains. More recently Miss Bourquin 

 (1917) asserts that the pyrenoid has nothing to do with the appearance 

 of starch, the body of the chromatophore alone being concerned. She 

 observes the starch grains appearing first near the periphery of the 

 chromatophore entirely apart from the pyrenoid, the later formed grains 

 differentiating in positions progressively nearer the pyrenoid (Fig. 38, B). 



The pyrenoid of Anthoceros (Fig. 37, C) as described by McAllister 

 (1914) is in reality a group of about 25-300 small "pyrenoid bodies" 

 which are probably composed of a protein substance. The outermost 

 bodies become starch, new ones apparently being formed by the fission 

 of those lying on the interior of the group. McAllister states that no 

 pyrenoid is visible in the young sporogenous tissue, starch being formed 

 without its aid. Somewhat later several small bodies appear and 

 aggregate to form the pyrenoid. 



Cleland (1919) recently reports a close association of the pyrenoid 

 of Nemalion with the formation of Floridean starch. 



Elaioplasts and Oil Bodies. In 1888 Wakker discovered in the cells 

 of Vanilla planifolia and V. aromatica certain plastid-like bodies to 

 which he gave the name elaioplasts, since they seemed to be concerned in 



