934 



SCIENCE. 



[N. S. Vol. XI. No. 285. 



rootg. (epidermis) of Saxifraga, CEnothera, 

 Xanthoxylon, aud Thesium; fruits (epidermis) 

 of Punica and Camellia. In the roots and 

 fruits it seems to occur less frequently than 

 in leaves and flowers, especially frequent 

 is the occurrence in the epidermis and 

 the fibro-vascular tissue. * Leaves in the 

 shade contain less than those exposed to 

 light, while leaves with partial albinism 

 may contain in the white parts as much as 

 in the green. In plants exposed to starva- 

 tion by being kept in darkness it is gradu- 

 ally consumed with production of amido 

 compounds. 



It is generally stored up in the vacuole, 

 but in some cases also in the cytoplasm. 

 The method of proving its presence consists 

 in the application of dilute solutions (0.5%) 

 of weak organic bases as caifeine and anti- 

 pyrine. These can easily enter the cells 

 without killing the protoplasm immediately 

 and can separate the active albumin in form 

 of little globules which coalesce gradually 

 to larger bright droplets 

 whose changes by various 

 reagents can easily be fol- 

 lowed under the micro- 

 scope. 



Generally it will suffice 

 to place small pieces of 

 vegetable tissue in a few 

 drops of caffeine solution 

 and then tear them up into 

 finer fragments by the aid 

 of dissecting needles. In 

 other cases it is preferable 

 to let the caffeine solution 

 act for a number of hours. 

 These globular formations were designated 

 by us as proteosomes. When the objects 

 soon after tiie formation of the proteosomes 

 are replaced in water the droplets will grad- 



* Especially noticeable is the large amount pres- 

 ent in insectivorous plants, Utricularia alone being 

 devoid of it. In Cephalotus the large amount is es- 

 pecially remarkable. Drosera shows it not only in 

 the leaf but also in stem and flower. 



ually disappear again in proportion as the 

 caffeine or antipyrine leaves the cells again 

 by osmosis. Return of the objects to the 

 former solutions makes the droplets re- 

 appear. When, however, the cells die 

 gradually or are killed by iodine solution 

 or acids in high dilution, or by for- 

 maldehyde, hydroxylamine, diamidogen, 

 prussic acid, free cyanogen, or salts of cop- 

 per, or by vapors of ether, these droplets 

 change their properties, becoming vacuo- 

 lized, insoluble, and solid. Generally they 

 become at first turbid from innumerable 

 little vacuoles which in mostcasesunite soon 

 and form one large vacuole, thus producing a 

 hollow sphere representing itself under the 

 microscope as a ring. If now the objects 

 are placed again in water these changed 

 proteosomes will not dissolve as they did 

 before. The coagulation by heat is easily 

 observed on dipping the objects in boiling 

 water containing 5 per cent, of sodium 

 chlorid. A change somewhat different ig. 



Fro. 1. Fig. 2. 



Fig. 1. Subepidermal cells of the lower side of the leaf of Ech- 

 evera, after treatment with caffeine. 



Fig. 2. Cells of Spirogyra treated with caffeine. The proteo- 

 somes produced show beginning vacnolization. 



brought on by highly dilute ammonia of 1 

 per mille or less, inasmuch as the proteo- 

 somes thereby shrink and solidify but gen- 

 erally do not vacuolize as in the above 

 cases.* 



* A full description of the proteosomes is given in 

 Chapters 9 and 10 of my treatise: 'Die chemische 

 Energie der lebenden Zellen,' Munich, 1899. E. 

 Wolff, publisher.. 



