MORPHOLOGY 79 



ETHEREAL OILS AND RESINS. In many cases the strongly refractive drops 

 found dispersed throughout the cytoplasm are globules of some ethereal oil. It is 

 the presence of such oils in the petals of many flowers that gives to them their 

 agreeable perfume. Under certain conditions the oil globules may become crystal- 

 lised. This occurs, for example, in Rose petals. In 7iio.st cases ethereal oils or 

 resins are formed in special protuberances ( 76 ) or strata ( 77 ) of the cell wall and only 

 later are stored in the interior of the cell or in special intercellular spaces formed 

 hy separation or destruction of cells. Special cells of this kind, often with corky 

 walls and filled with resin or ethereal oils, are found in the rhizomes of certain 

 plants, as for instance -in those of Acorus Calamus and of Ginger (Zingibcr 

 qfficinalc) : also in the bark, as, for example, of Cinnamon trees (Cinna'niomum) ; 

 iu the leaves, as in the Sweet Bay (Laurus nolnlis) ; in the pericarp and seed of 

 the Pepper (Piper niyrum) ; in the pericarp of Anise (Illicium anisatwn). 



Mn ILACJK is often found in the cells of bulbs, as in Alt turn Cepa and L'njiimi 

 Xcilla, in the tubers of Orchids, also in aerial organs, especially in the leaves of 

 succulents, which, living in dry places, are thus enabled to maintain their water 

 supply by means of their mucilaginous cells. 



CAOUTCHOUC AND GUTTA-PKRCHA. These substances are found in a number of 

 plants belonging to different groups, in particular in the Moraceae, Euphorbiaceae, 

 and Sapotaceae. They occur in the latex of special cells in the form of small 

 globules, which, suspended in the watery sap, give it its milky appearance. 



FERMENTS. Bodies of this nature are widely spread in vegetable cells. Their 

 significance in the oxidation processes taking place in the organism has been dealt 

 with by R. CHODAT, A. BACH ( 78 ), and others. The name leptomin was given 

 by RACIHOUSKI (~ 9 ) to a catalytic enzyme, which he found in the sieve-tubes and 

 laticiferous elements of the higher plants, in the milk of the coco-nut, and in|the 

 tissues of the potato tuber. 



SULPHUR. The presence of sulphur in the form of small refractive grains in 

 the protoplasm of certain Bacteria, the Beggiatoae, is noteworthy. These Bacteria 

 live in water containing much organic matter, and, according to WINOGRAPSKY I 80 ), 

 obtain their sulphur from sulphuretted hydrogen. In fulfilling its function in the 

 Bacteria the sulphur becomes oxidised into sulphuric acid. 



The Cell Sap. Under this term is included especially the fluid 

 which in old cells fills the inner sap cavity. It is generally more 

 watery and clearer than the fluid contained in the smaller vacuoles 

 of the cytoplasm. No sharp distinction can, however, be drawn 

 between the sap cavity and vacuoles, and, moreover, a number of 

 such vacuoles may take the place of the sap cavity itself. The cell 

 sap usually gives an acid reaction, owing to the presence in it of 

 organic acids or their salts. The substances held in solution by the 

 cell sap are very various. The soluble carbohydrates, in particular 

 the sugars (cane sugar, the glucoses, and especially grape sugar), 

 frequently occur in the cell sap. The glucoses may be recognised by 

 their reducing properties. 



If preparations containing glucose be placed in a solution of copper sulphate, 

 and, after being washed out, are transferred to a solution of caustic potash and 

 heated to boiling, they will give a brick-red precipitate of cuprous oxide. If cane 

 .sugar or saccharose be present, this same treatment gives only a blue colour to the 

 cell sap. 



