64 MORPHOLOGY OF THE CELL. 



minutely, and has ascertained (as Lebreton also thought, see Husemann, Die Pflanzen- 

 stoffe, p. 709) that they consist of Hesperidin. It is remarkable that only some indi- 

 viduals of the species named yield sphere-crystals, as for instance those in the botanical 

 garden at Wiirzburg ; a tree in the garden at Marburg yielded them in its unripe fruits 

 in 1 87 1, but not since. Sphere-crystals of organic structure (combustible), but of 

 otherwise unknown constitution, have also been described by Kraus and Russow; the 

 former found them in the epidermis of the leaves and stem of Cocculus laurifolius, on 

 treatment of the fresh cells with alcohol, glycerin, or even water. Russow ^ found, in 

 the living cells of the petiole and mesophyll of Marattia cicutcpfolia and Angiopteris erecta, 

 sphere-crystals which enclosed a small crystal or other minute body as a central nucleus. 

 Where the living cells did not contain these structures, he obtained them by treatment 

 with alcohol ; they left behind, on combustion, a considerable quantity of ash. Russow 

 also found similar bodies in the cortex of Selaginella Martensii and in tropical orchids, 

 when the plants had lain for some time in alcohol. He states that all these sphere- 

 crystals have the property of staining with carmine. 



In the cell-sap of the Hepaticae there occur vesicles or nodules of a peculiar 

 appearance. In a letter PfefFer states that they are formed in the very young leaves 

 of Jungermannieae [Alicularia scolaris, Radula complanata, &c.) by the coalescence or 

 grouping together of minute drops of oil, which are first formed in the cell-sap, not 

 in the protoplasm, and must be regarded as products of excretion which have no 

 further purpose in assisting growth ; as is the case also with the fatty oils which are 

 stored up as reserve-materials. A membrane-like envelope surrounds these drops of 

 oil, whose substance consists, in addition to oil, of water and small quantities of 

 proteids. Of a similar nature are the bodies found in the thallus of the Mar- 

 chantiese, which, in the case of Lunularia, also contain tannin. 



Among other organised constituents of the cell-sap must be mentioned the spherical 

 drops or granules containing tannin and surrounded by a thin membrane which are 

 found in particular cells of the cortex of many plants rich in tannin, as Salix, Betula, 

 Alnus, Quercusj Sec. (see Nageli u. Schwendener, Das Mikroskop, p. 492). They are still 

 more conspicuous in the motile parts of the leaves of the sensitive plant, where 

 Pfeffer^ has investigated them with care. Here they consist of a thin but tolerably 

 firm membrane, enclosing a concentrated solution which contains a large quantity of 

 tannin. The strongly refractive contents of the spherical bodies are coloured blue by 

 solutions of iron, and form a reddish-brown mass with potassium bichromate. If the 

 contents are extracted with water containing alkali, acid, or alcohol, the membrane 

 is left, and is perhaps what has been termed a 'pellicle-precipitate,' consisting of a 

 combination of tannin with a proteid^. PfefFer states that spherical bodies of 

 this nature are found in particular cells of the cortex of the stem and petiole of 

 the sensitive plant, as well as in the petioles of Oxalis stricta and Acetosella; ac- 

 cording to Meyen they occur also in Desmodium gyrans ; and, according to Unger, in 

 Glycyrrhiz.a. 



Sect. ii. Crystals in the Cells of Plants'*. — The crystal-like forms de- 

 scribed in Sect. 7, in which proteids are sometimes found, though always mixed 

 with other organic compounds, are not common phenomena, and must not be 

 placed in the same category as the very abundant true crystals of lime salts now 



^ Untersuchungen liber die Leitbiindelkryptogamen, Petersburg, 1872, p. 109. 



^ Physiol, Untersuch., pt. I, Ueber Reizbarkeit, Leipzig 1873, p. 13 et seq. 



^ See Book III. Chap. i. Sect, i, Traube's artificial cells. 



* Sanio, Monatsber, der Berl. Akad., April 1857, p. 254. — Hanstein, ibid. Nov. 17, 1859. — 

 Holzner, Flora, 1864, pp. 273, 556, and 1867, p. 499. — Hilgers, Jahrbuch fiir wiss. Bot. vol. VI, 

 1867, p. 285. — Rosanoff, Bot. Zeitg. 1865 and 1867. — Solms-Laubach, Bot. Zeitg. 1871, nos. 31-33. 

 — Pfitzer, Flora, 1872, p. 97. 



