Chapter XVIII 



LIPIDE GRANULES, MICROSOMES AND 

 OTHER METABOLIC PRODUCTS 



Observation of living material in most, if not all, plants shows 

 that there exist in the cytoplasm in addition to the elements dis- 

 cussed above, certain small granules, spherical in shape, which 

 we call lipide granules. These granules have often been 

 confused with mitochondria. In living cells observed in direct 

 illumination, they are the most clearly visible of all the cytoplasmic 

 inclusions because of their high refractivity. They are still more 

 distinct with lateral illumination, under which circumstances they 

 are usually the only visible elements of the cytoplasm. They appear 

 strongly lighted against the black background (the cytoplasm) on 



which they can very distinctly be seen 

 to move. With the Zeiss micropolychro- 

 mar they can very clearly be seen to 

 have a color different from that of the 

 cytoplasm and much more accentuated 

 than that of the chondriosomes. The 

 lipide granules are distinguished very 

 sharply from the mitochondria by 

 their high refractivity, by their very 

 rapid displacements in the cytoplasmic 

 currents and by the variability of their 

 size. The smallest have a size in- 

 ferior to that of mitochondria and the 

 largest may greatly exceed it. These 

 granules are distinguished from the 

 mitochondria also by their osmium- 

 reducing properties. 



In some cases they may agglomerate 

 in mulberry-shaped masses or in little 

 chains and fuse to become huge globules. It seems that most of 

 the bodies described as oleoplasts or elaioplasts correspond to ag- 

 glomerations of granules of this nature formed under influences 

 as yet unknown. In each epidermal cell of the leaf of Vanilla 

 planifoUa, Wakker first called attention to a voluminous body 

 which he called an elaioplast. It is generally larger than the nu- 

 cleus and is localized in the cytoplasm and in the neighborhood of 

 the nucleus. This body is irregular in shape and composed of very 

 numerous small lipide droplets which according to Wakker are 

 enclosed in a protein film. These bodies, which were thought to be 

 plastids elaborating lipides, have also been found in the epidermis 

 and other tissues of many plants, especially of the Monocotyledons 

 (Fig. 142). They cannot however be considered as plastids. In 

 the epidermis of tulip, each cell encloses a large fatty body which 



Fig. 139. — Tulip. Epidermal 

 cell of leaf under the ultramicro- 

 scope. Only the lipide granules 

 (G) carried about in the cyto- 

 plasmic trabeculae are visible. 

 O, fatty body. 



