26o (;IJMPSES I\TO PLANT-LIFE 



cot)'ledons. Lea\int( our seeds for a day or two 

 longer we find a further change. The j^kunule 

 has been carried up beyond the soil-level and has 

 begun to expand into leafage. It is interesting to 

 note how the curved tigcllnm, jDushing through the 

 soil first, effectually guards the plumule from 

 injur)' arising from contact with rough particles 

 of earth ; the cotyledons remain just below the 

 soil-level and wc see that the tigellnin is thicken- 

 ing and forming a distinct connecting branch 

 between the new shoots and the fleshy seed leaves ; 

 these latter are full of plant food, and the jjlumule 

 is supplied from this storehouse of nutriment imtil 

 the first lea\es are formed and are able to de- 

 compose carbon-dioxide for the nourishment of 

 the plantlet. The seed-leaves in this case do not 

 perform this function, but act simply as store- 

 houses. 



Our next seed example will be the familiar 

 mustard plant. These we may sow in two lots, 

 the first we only need to sprinkle upon some fine 

 soil and the second may be sown in a shallow drill 

 and covered with fine earth. 



The first sowing will quickl)- germinate, and the 



