i6 BOTANY AND PHARMACOGNOSY. 



made up of the valves of diatoms, is used chiefly as an absorbent 

 agent for storing nitroglycerin, as in the production of dynamite. 

 Being a non-conductor of heat the material also finds use in the 

 rnanufacture of the so-called isolation plates for machinery. 

 Another use is as a tooth powder. Among the Chinese and Lap- 

 landers diatomaceous earth has also been used as an edible, earth 

 known as '" mountain meal " or " bread-stone." It has been used 

 in India as a rubefacient. 



Many of the Algse are of use as food, of which the following 

 may be mentioned : Vaucheria fastigiata, GriMthsia coralina, 

 Ceramium Loureirii, Chondrus crispus (Fig. 9), Gigartina niamil- 

 losa (Fig. 278a), Gelidiuin cartilagiiieum, Gelidium criitale (yield- 

 ing agar-agar), Rhodyincnia palmata (yielding dulce), and sev- 

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



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

 as Durvillcza iitilis, Ascophyllum nodosum, Fucus vesiciilosus 

 (Fig. 9, illus. 2), Sargassum linifolium, Laminaria saccharina, 

 Laminaria digitata, Alaria esculenta, Rhodymenia palmata, Phyl- 

 lophora membranifolia, Macrocystis pyrifera, and Fastigiaria fur- 

 cellata. 



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

 for phthisis, as Fucus cartilagineits, Stilophora rhisodes 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 Algse 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 ftlum, 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 materials, 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 



