110 



INTRODUCTION TO CYTOLOGY 



the elaboration of oil (Fig. 40, A}. They were soon observed in a number 

 of monocotyledons by Zimmermann (1893), Raciborski (1893), and Kiis- 

 ter (1894); and some time later in the flower parts of a dicotyledon, 

 Gaillardia, by Beer (1909). Politis (1914) has found them in monocoty- 

 ledonous plants belonging to 19 different genera, and in five genera of 

 dicotyledons (Malvaceae). 



There is a considerable lack of agreement in the opinions expressed 

 on the subject of the origin and significance of elaioplasts. Wakker 

 thought it probable that they represent meta- 

 morphosed chloroplasts, which they often closely 

 resemble in structure (Kiister), whereas Raciborski 

 asserted that they arise as small refractive gran- 

 ules in the cytoplasm and multiply by budding. 

 In the zygospores of Sporodinia grandis and 

 Phycomyces nitens Miss Keene (1914, 1919) reports 

 the presence of a number of globular structures 

 with which oil is associated from their earliest 

 stages. These unite to form one or two large 

 reticulate bodies which Miss Keene believes are 

 related to the elaioplasts of higher plants. All of 

 these investigators, with Politis, agree that elaio- 

 plasts are normal cell organs with a special func- 

 tion, namely, the formation of oily substances 

 having a role in nutrition. Beer, on the contrary, 

 states that in Gaillardia they are formed secon- 

 darily by the aggregation of many small degen- 

 erating plastids and their products at one or 

 more points in the cell, all stages of the process 

 being observed. Although the bodies so formed 

 may, if green, produce starch, or, if colorless, an 

 oily yellow pigment, Beer thinks it probable that 

 they have no important special function in the life 

 of the plant. 



Closely associated with investigations on elaioplasts have been those 

 concerned with the oil bodies found in the cells of many liverworts (Fig. 

 40, B). These bodies, discovered by Gottsche in 1843, were first carefully 

 described by Pfeffer (1874). Pfeft'er stated that they arise by the fusion 

 of many minute droplets of fatty oil appearing in the cytoplasm of very 

 young cells, and later come to lie in the cell sap; he further believed them 

 to possess a special membrane. Wakker (1888) held them to be analo- 

 gous to leucoplasts and chloroplasts, multiplying by fission at each 

 cell-division, and pointed out that they lie in the cytoplasm rather than in 

 the cell sap. He was inclined to view them as products of elaioplasts, 

 which Ktister (1894) supposed them to resemble in having a spongy 

 stroma containing oil in the form of minute droplets. 



FIG. 40. 



A, elaioplast forming 

 oil droplets in epidermal 

 cell of perianth of Poli- 

 anthes tuberosa; nucleus 

 with small plastids at 

 right. (After Politis, 

 1914.) B, oil bodies in 

 various stages of develop- 

 ment in a cell of Caly- 

 pogeia. (After Gargeanne, 

 1903.) 



