ORIGIN AND MORPHOLOGY OP CHLOROPRTLL CORPUSCLES. 241 



or tissues ia which they are included, or, in other words, they 

 are capable of a varying metamorphosis. Some of them remain 

 as Leukoplastids, and serve for the formation of starch at the 

 expense of substances already assimilated ; or they become Chlo- 

 roplastids in green-coloured parts ; or finally, in flowers or 

 fruits, they assume various colours, and appear as Chromoplas- 

 tids. Further, as above implied, one and the same plastid 

 appears to be capable of various metamorphoses ; thus, Leuko- 

 plastids may develope as chlorophyll grains, and subsequently 

 lose their green colouring matter, and assume the character of 

 Chromoplastids. Lastly, it has been observed in the fruit of 

 Symphoricarpus racemosus that Chloroplastids may be 

 again transformed into Leukoplastids, and the same is the case 

 in many embryos. 



Some plastids have an active life ; they assimilate, or produce 

 starch at the expense of materials already assimilated, they 

 form pigments, multiply by division, &c. But there are also 

 plastids which have temporarily or permanently little or no 

 vital function. This is the case with many Leukoplastids, 

 especially those found in the epidermis of most plants, and also 

 the colouring bodies of flowers and fruits. With this passive 

 character the plastids assume more or less crystalline forms and 

 are also doubly refractive. (Figs. 8 — 14). The active plastids 

 are, however, always round in the higher plants. Schimper 

 further describes how tlie originally round active plastid 

 becomes transformed, rapidly or slowly in various cases, into the 

 angular, crystal-like plastid (compare Figs.), and how conversely 

 the crystal-like plastid may again resume the spherical form 

 when it again begins to exercise active vital functions. He 

 finds himself convinced that we have here to do with a true 

 process of crystallisation, and that the angular plastids not 

 only have an external similarity to crystals, but actually are 

 true crystals. 



In the main points these results are supported by the inde- 

 pendent observations of Prof. Strasburger, and A. Meyer. 



I 'Bot. Centralbl.,' 1882, No. 48, " Ueber Chlorophyllkorner, Starkebildner, 

 und Farbkorper," ' Das Chlorophyllkorn,' Leipzig, July, 1883, Felix. 



