40 A TEXT-BOOK OF BOTANY. 



most fertile parts of the globe. It is a saying even among the 

 most distant of the different tribes living on the Orinoco, when 

 speaking of anything very unclean, that it is " so dirty that the 

 Otomacs eat it." 



ECONOMIC USES OF ALG^:. Many of the Algae are of use as 

 food, of which the following may be mentioned : Vaucheria fasti- 

 giata, GrMthsia coralina, Ceramium Loureirii, Chondrus crispus, 

 Gigartina mamillosa, Gelidium cartilagineum, Gelidium crinale 

 (yielding agar-agar), Rhodymenia palmata (yielding dulse), and 

 several species of Gracilaria (which also yield agar-agar). 



Some of the sea-weeds are used in the production of iodine, 

 as Durvillcea utilis, Ascophyllum nodosum, Fucus vesiculosus 

 (bladder-wrack), Sargassum linifolium, Laminaria saccharina, 

 Laminaria digitata, Alaria esculenta, Rhodymenia palmata, Phyl- 

 lophora membranifolia, Macrocystis pyrifera, and Fastigiaria 

 furcellata. 



A number of the Algae are also used in medicine, particularly 

 for phthisis, as Fucus cartilagineus, Stilophora rhizodes and 

 Dictyopteris polypodioides. Alaria esculenta and Laminaria digi- 

 tata are used in the making of bougies and tents used in surgery. 

 Owing to the toughness of some of the Algae on drying, the 

 material is used in the manufacture of various articles, as handles 

 for tools from the thick stem of Lessonia fucescens, fishing lines 

 from Chordaria ftagelliformis (Fig. 20), etc. 



FUNGI. 



The Fungi form a large group of plants which do not produce 

 chloroplasts or any bodies having a similar function. They have 

 not the power of carbon dioxide assimilation, that is, unlike the 

 Algae, they are unable to manufacture food materi'als, such as 

 carbohydrates (starches, sugars, etc.), from carbon dioxide and 

 water. Hence they are dependent upon previously formed food 

 products, and may derive their food from living plants or ani- 

 mals, when they are known as PARASITES, or from decaying animal 

 or vegetable matter, when they are known as SAPROPHYTES. The 

 living plant or animal atacked by a fungus is known as the host. 



Fungi are especially characterized by the habit of arising 

 from spores and of producing thread-like cells the growing point 



