sect. I MORPHOLOGY 73 



this form. But fatty substances may also appear in the cytoplasm as 

 irregularly-shaped, more or less soft grains, as for example in the 

 vegetable butters and in the wax of various seeds ; they may even 

 be crystalline, as in the needle-like crystals of Para-nuts (Bertholletia 

 excelsa) and of Nutmeg (Myristica fragrans). 



Glycogen. — This substance, related to sugar and starch, and of frequent occur- 

 rence in animal tissues, fulfils, according to Errera, the same functions in the 

 Fungi as sugar and starcli in the higher plants. Cytoplasm containing glycogen 

 is coloured a reddish-brown with a solution of iodine. This colour almost wholly 

 disappears if the preparation be warmed, but reappears on cooling. 



Ethereal Oils and Resins. — In most cases the strongly refractive 

 drops found dispersed throughout cytoplasm are globules of some 

 ethereal oil. It is the presence of such oils in the petals of many 

 flowers that give to them their' agreeable perfume. Under certain 

 conditions the oil globules may become crystallised. This occurs, for 

 example, in Rose petals. Secretions from surrounding cells are often 

 deposited in special receptacles in which, through oxidisation, camphor 

 or resin is formed. 



Special cells of this kind, with corky walls and filled with resin or ethereal 

 oils, are found in the rhizomes of certain plants, as for instance in those of 

 Calamus (Acorus Calamus) and of Ginger (Zingiber officinale) ; also in the bark, 

 as, for example, of Cinnamon trees (Cinnamomum) ; in the leaves, as in the Sweet 

 Bay (Laurus nobilis) ; in the pericarp and seed of the Pepper (Piper nigrum) ; 

 in the pericarp of Anise seeds (Illicium anisatum). 



Mucilaginous Matter is often found as a part of the cell contents 

 in the cells of bulbs, as in Allium Cepa and Scilla maritima, 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-percha. — These substances are found in 

 a number of plants belonging to different groups, in particular in the 

 Urticaceae, Eupkorliacme, and Sapotaceae. They occur in the so-called 

 milk sap of special cells in the form of small, dense globules, which, 

 suspended in the watery cytoplasm, give it its milky appearance. 



Sulphur. — As being of unusual occurrence, mention should be made of the 

 presence of sulphur in the form of small refractive grains in the protoplasm of 

 certain Bacteria, the Beggiatoae. These Bacteria live in water containing much 

 organic matter, and, according to Winogradsky, 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 watery 

 and clearer than the fluid contained in the smaller vacuoles of the 



