TISSUES AND SIMPLE ORGANS. 



143 



nation (Fig. 83). Strictly considered, this is really a case which 

 serves for the circulation and utilization of the assimilated food- 

 substances in one and the same plant, and not for the appropriation 

 of food- substances from the outside. 



4. The cotyledons at first serve as organs to absorb the endo- 

 sperm, and subsequently become organs of assimilation (see Fig. 

 84, which represents a seedling of Pinus Pineal) 



FIG. 83. Bean-seedling. 

 (After Krass and Landois.) 



FIG. 84. Seedling of Pinus Pinea. 



w and mv, Roots : c, cotyledons ; he, hypocoty- 

 ledonous stem (radicle); s, outer seed-coat; 

 r, inner seed-coat. (After Berthold and Lan- 

 dois.) 



5. The cotyledons contain some food-material and begin the 

 function of assimilation as soon as the reserve food is assimilated. 

 The endosperm is wanting. The cotyledons soon become green 

 (Oruciferce). This case, like number 3, is introduced for the sake 

 of completeness. 



(b) Nutrition of Saprophytes and Parasites. 



The term ' ' parasite ' ' in itself indicates that the organisms 

 referred to require an organic substratum upon which to live. The 

 assimilation of food-substances prepared by life-processes is common 



