ROOTS 



107 



food supplies. 

 T h e r G f o r o , p r o - 

 cesses are devel- 

 oped "which pene- 

 trate and aliscirh. 

 The mistletoe and 

 dodder are seed- 

 plants "whieh have 

 t h i s h a Ij it. a n d 

 both have such 

 processes (see Figs. 

 102, 103). This 

 habit is mncli more 

 extensively devel- 

 oped, however, in 

 a low group of 

 plants known as 

 the fungi. Many 

 of these iiarasitic 

 fungi live upon 

 jilants and animals, 

 common illustrations being the mildews of lilac leaves and 

 many other plants, the rust of wheat, the smut i:if corn, etc. 



70. Root structure. 

 — In the lowest groups 

 of plants (alg;e. fungi, 

 and moss-plants) true 

 roots are not formed, 

 but very simple struc- 

 tures, generallv hair- 

 like (see Fig. 104). In 

 fern-plants and seed- 

 plants, however, the 

 root is a complex 

 structure, so different 

 from the root-like pro- 



FiG. 103. A section eliowing the Ihin^ fonnection 

 between dodder .and a golden rod upon whicli it is 

 trrowing. The penetrating and absorbing organ (//) 

 has passed tlirouLdi the cortex ic). the vascular 

 zone (/_*), and is disorganizing the jjith (i>}. 



riG. 104. Section through the thallus of a li\er- 

 wort Ofcii'chaiifia), showing the hair-like pro- 

 cesses (rhizoidsJ wliich come from the under 

 surface and act as roots in gripping and ab- 

 sorbing. In the epidermis of the upper surface 

 a chimney-iike opening is seen, leading into 

 a chamber containing cells with chloroplasts. 



