PHYSIOLOGY 35 



The development of the elaioplasts of Gaillardia has been 

 followed by Beer,* who found that they are formed by the 

 aggregation of chloroplasts which then degenerate and give 

 origin to the oil. He considers it is most unlikely that elaio- 

 plasts perform any function of direct importance to the life of 

 the plant, although they may in some cases, the corolla-hairs 

 of Gaillardia, for instance, serve a biological purpose. 



Elaioplasts are not, by any means, always present. Rivett f 

 from her study of Alicularia scalaris, a liverwort, concludes 

 that in this instance the fat originates as a general proto- 

 plasmic secretion, not from an elaioplast or other special body. 

 It is a secondary product, its production being unaffected by 

 changes in the cultural conditions brought about by variations 

 in illumination, temperature, and nutritive materials. 



Although elaioplasts may not perform the function origin- 

 ally ascribed to them, it does not necessarily follow that 

 fats, more especially when occurring in the green parts of 

 plants, may not be direct photosynthetic products. Thus 

 Fleissig considers that in the case of Vaucheria, the abundant 

 fat-like substance is a direct photosynthetic product com- 

 parable to the starch and sugar in ordinary green leaves. 

 On the other hand, it is possible that the fats in such cases 

 may have been produced by secondary changes in the original 

 product of photosynthesis. 



The fat-economy of Vaucheria, however, requires further 

 investigation ; thus Meyer % states that the oil drops are 

 produced by the chloroplasts and result from the photo- 

 synthetic processes ; they are not, however, fats in that they 

 do not give characteristic microchemical reactions. Similarly 

 the oil bodies described as occurring in the mesophyll of- 

 Ilex, Kalmia, Taxus, Tropceohim, and Vinca, which increase in 

 size with the age of the leaf, do not give characteristic fat 

 reactions. Mangenot § describes two kinds of oil drops in 

 Vaucheria : spherical drops of various sizes associated with 



* Beer : " Ann. Bot.," 1909, 23, 63. 

 t Rivett : id., 1918, 32, 207. 



J Meyer : " Ber. deut. bot. Gesells.," 1917. 35, 586 ; 1918, 36, 5, 235, 

 674. 



§ Mangenot : " Compt. rend. soc. biol.," 1920, 83, 982. 



3* 



