278 INTRODUCTION TO PLANT GEOGRAPHY [CHAP. 



Floriculture, the branch of horticulture concerned with the com- 

 mercial production of flowers, is really a huge industry that is 

 important on an ahnost world-wide scale, but especially in the 

 temperate zone. The actual growing is often scientifically regulated 

 in many ways, as in greenhouses, and the organization for transport 

 and selling is complex and vast. Lawn-growing and landscaping 

 are also of considerable importance in urban areas and elsewhere, 

 for recreational and ornamental purposes ; their primary function, 

 however, is the growing of plants. All this, moreover, involves 

 extensive trading in seeds, bulbs, etc., and sometimes in apparatus 

 for plant growth — for example in hydroponics, their cultivation 

 without soil. 



Microorganisms and Miscellaneous 



We have already mentioned the importance of some micro- 

 organisms in affording drugs (such as penicillin) and foods (such 

 as Food Yeast), and, towards the end of the last chapter, in causing 

 plant diseases. Others are of vast importance in bringing about 

 desirable changes — for example the Yeasts in causing fermentation 

 of sugars to alcohols, and various Bacteria in effecting further 

 fermentation to vinegar as well as in the ' curing ' of tobaccos and 

 ' ripening ' of cheeses. On the positive side, further valuable 

 fermentation, fibre-retting, organic acid and vitamin production, 

 hide-dehairing, nitrogen-fixing, sewage-disposal, purification and 

 preservation, cooking and silage and all manner of other operations 

 are carried out only by or with the aid of microorganisms. On the 

 negative side, there are the numerous human and other animal 

 diseases which they cause, as well as loss by rotting, putrefaction, 

 and general decay. These last activities involve the breakdown of 

 complex carbohydrate and other materials to simpler ones and 

 ultimately to the raw materials whence they came. Such ' degrada- 

 tion ' is essential to keep the world going, for without it the vital 

 raw materials such as carbon dioxide would all be used up sooner 

 or later and life would come to a standstill. Consequently non- 

 green microorganisms, which are almost entirely responsible for the 

 breakdown and return of the essentials to general circulation, are 

 the world's great scavengers, and, as such, are of fundamental 

 importance to all life. 



Nor, among microorganisms, must we overlook the smaller Algae, 

 which possess chlorophyll and so are able to build up complex 



