INTRODUCTION 13 



and the rootlets or rhizoids serve merely, perhaps, 

 as a means of keeping the plant properly poised 

 Some floating types, moreover, are rootless. 



Upon the root are root-hairs. These are all- 

 important in the absorption of water from the soil, 

 and it is through the cellulose non-cuticularised walls 

 of these that the water passes. 



This applies to annuals and trees. In the case of 

 many perennials, whose aerial parts die down in 

 winter, especially tuberous-rooted plants, the root 

 itself stores up material, or this may be done by 

 specialised stem structures, such as rhizomes, bulbs, 

 corms, tubers, which are commonly confounded with 

 roots. But these are enlarged underground stem- 

 bases, and roots proper, with root-hairs, are also 

 found attached to them. 



Parasitical plants are rooted in or on other plants, 

 and whilst possessing root-hairs, derive their water 

 or nutrient solutions from their host. In the case of 

 saprophytes which live on decaying organic matter, 

 the already elaborated materials of the host (or 

 mycelium) are transferred by the roots. Epiphytes 

 live on trees attached to their host. Some roots are 

 used for climbing, as in the Ivy, a sort of epiphyte. 

 The mistletoe receives the ascending sap and so lives 

 as a parasite, whilst being also green or yellow it 

 manufactures its own carbohydrates, but only to a 

 small extent. 



The stem, as has been seen in the case of tissues, 

 serves as a means of transport of water and nutrient 



