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 Pinea.) 



ho 



Fig. 83.— Beau-seedling. 

 (After Krass and Laudois.) 



Fig. 84. — Seedling of Pinus Pinea. 



w and nil', Roots ; c, cotyledons ; he, hypocoty- 

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

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

 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 

 {OrucifercB). Tins case, like number 3, is introduced for the sake 

 of completeness. 



(h) 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 



