DICOTYLEDONS MELON AND BEAN 53 



separate plants from animals. The embryo, of at any 

 rate one of the higher animals, expands after birth* 

 while that of a flowering plant remains practically the 

 same size, becoming the mature plant only by the_ 

 addition of new organs. 



3. Now look at the pot containing the Gram or the 

 Brown-bean seeds. Here again, the first sign of the 

 new plant is an arched axis which pushes up the soil, 

 and breaking its way through, at length emerges, and as 

 it straightens, pulls up out of the seed two thick flat 

 bodies. Between them is a bud, which soon develops 

 as a shoot axis with two green leaves at the top, each 

 folded along its middle line, and one inside the fold 

 of the other. These being exactly like the later 

 ones are the first normal leaves and correspond to 

 the first rough leaves of the Melon. So that the 

 two thick white bodies correspond to the cotyledons* 

 Indeed, while still in the seed, they are in no essen- 

 tial point different. But those of the Melon turn 

 green, and are thus able to make food for the young 

 plant soon after they have emerged from the ground, 

 while the cotyledons of the Bean are thicker and 

 contain so much ready-made food- material given to 

 them by the mother-plant, that they can, without turning 

 green, supply food at once to the seedling. 



It is perhaps because of this that the shoot-bud of 

 the Bean is larger and develops more quickly than does 

 that of the Melon. It would seem indeed, as if there 

 were no necessity for the cotyledons of the Brown- 

 bean or Gram to leave the seed at all, because, being 

 colourless, they can gain nothing from the light and 

 air, and might as well stay underground. 



