Chapter XVIII 



205 — 



Lipide Granules 



Fatty degeneration:- Fatty degeneration which is exhibited by 

 many cells at the end of their development, especially in the fungi, 

 is also brought about by the increasingly large production of 

 granules, similar to the microsomes, which run together into 

 large globules. This process seems to correspond to a lipophanero- 

 sis i.e., a breaking down of the lipides, of the lipoprotein com- 

 pounds which comprise the cytoplasm. 



Essential oils and resins likewise appear as small globules in 

 the cytoplasm and their very refractive appearance and their histo- 

 chemical reactions greatly resemble those of the lipide granules, 

 from which they are only with difficulty distinguished. 



-C«. 



Other metabolic products:- The cytoplasm of plant cells may 

 contain a great number of other substances arising from cellular 

 metabolism. These substances, however, are not constant like 

 those mentioned above and are de- 

 termined by certain physiological 

 states of the cell. Some of these 

 products are inclusions in the 

 cytoplasm. 



Among them must be men- 

 tioned that which is called florid- 

 ean starch or starch of the Rhodo- 

 phyceae. It differs essentially 

 from ordinary starch by the fact 

 that it is not formed in plastids 

 but appears in the cytoplasm. 

 This starch becomes visible in the 

 cytoplasm as granules of variable 

 dimensions, some extremely small, 

 a fraction of a fx, others of a diam- 

 eter which may exceed 20-30/i. 

 These variously shaped granules 

 (ovoid, plano-convex, bi-concave, discs etc.) are doubly refractive, 

 if they are large enough, and stain mahogany-brown to violet-red 

 with iodine. The chemical nature of this "floridean starch" is not 

 yet fully determined. It seems however that various substances 

 have been described under this name. Some of them, appearing 

 as rather large granules, correspond to a special variety of starch 

 (VAN TiEGHEM, Kylin). Others exist in the cytoplasm as a clus- 

 ter of minute granules capable even of emigrating into the vacu- 

 oles. Among these, some seem to be composed of a substance 

 related to the glycogens (Errera, Colin) ; others are products 

 (alkaloids) still imperfectly known (Gueguen). 



In the cytoplasm of the Euglenas are likewise found granules 

 of paramylum characteristic of the Phytoflagellates. These gran- 

 ules appear in the cytoplasm as discs, prisms, rods, stars and so 

 forth, showing alternately dark and light concentric layers like 

 the starch grains. They do not stain with iodine but have been 

 compared to starch. Mention must also be made of para-glycogen, 



Fig. 142. — Philodendron. Secretion 

 canal of an aerial root. C, lumen of the 

 canal; C.s., secreting cells; E, fatty se- 

 cretion blackened by osmic acid; M, chon- 

 driosomes; N, nucleus; P, plastids. Meves' 

 method with acid fuchsin. (After Miss 

 POPOVICI ) . 



