CHAPTER XXIX. 



MONOCOTYLEDONS. 



THE class Angiospermse includes the great mass of the flower- 

 ing plants. They differ from the gymnospermae in that they gen- 

 erally have the male and female organs in the same flower ; they 

 have the ovules in a closed ovary, and the flower differs more 

 widely from the other parts of the plant. 



The subclass monocotyledons has one cotyledon, parallel 

 veined leaves, and parts of the flower in threes, and the structure 

 of the stem differs from that of the dicotyledons. A cross section 

 of a stalk of Indian corn, which belongs to this group of plants, 

 shows it to be composed of parenchymatous tissue traversed 

 by great numbers of fibro-vascular bundles. These bundles are 

 more numerous toward the surface of the stem, so that it in- 

 creases in density from the center outwards, the central portion 

 often disappearing leaving a hollow stem, as in the grasses. 

 These bundles are closed bundles; as they become permanent 

 tissue no cambium or meristem tissue remains and no further de- 

 velopment is possible, and such plants are usually short-lived. 



The different stages of germination in these plants may be ob- 

 served by planting several grains of corn, and then by examining 

 a different grain every few hours the process may be followed 

 closely. The first leaf of the young plant has its dorsal surface 

 in contact with the endosperm or food supply, curving entirely 

 around the remainder of the embryo. As it begins to grow the 

 root pushes through the root sheath. The plumule, consisting 

 of a minute stem and a few rudimentary leaves, pushes out 

 through the curved cotyledon, which remains in contact with 

 the food supply, absorbing nourishment for the growing parts. 

 Make out these points from the study of the germinating grains, 

 making notes and sketches. 



The monocotyledons include about fifty natural orders of 

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