262 (iUMPSES INTO PLANT-] J I- E 



soil, and are thus enabled to counteract the fcMxe 

 exerted by the tip of the radicle; the latter j)ushes 

 through the ground without uplifting the seed. 

 This action can be watched and the growth of the 

 root-hairs observed by means of a pocket lens and 

 by the exercise of that virtue, most necessary for 

 all young naturalists — patience. 



Returning to the seeds that were sown under 

 the soil, we find the)' have germinated ; the radicle 

 is pushing downwards, and just above the soil- 

 level we ma}' see the short curved tigclliim. This 

 very quickly straightens itself, and then we ob- 

 serve that the cotyledons have been drawn out- 

 of the seed-coats and are displayed as two green 

 leaves, which in a few days will be an inch or two 

 above the ground, owing to the growth of the 

 tigelliun. Here we get quite a departure from the 

 bean seed, whose cotyledons were hjpogean (under 

 the earth), those of the mustard being epigean 

 (upon the earth). There is also another point of 

 difference; the mustard cotyledons are green, they 

 contain chlorophyll corpuscles, have stomates, and 

 so can perform all the functions of the normal 

 green leaf; thus they help at once to feed the 



