228 



General Biology 



Fig. 123. — Morphology of typical monoco- 

 tyledonous plant. A, leaf, parallel-veined ; B, 

 portion of stem, showing irregular distribu- 

 tion of vascular bundles; C, ground plan of 

 flower (the parts in 3's) ; D, top view of 

 flower; E, seed, showing monocotyledonous 

 embryo. (From C. Stuart Gager's "Funda- 

 mentals of Botany" by permission of P. 

 Blakiston's Son & Co., Publishers.) 



Fig. 124. — Morphology of a typical dico- 

 tyledonous plant. A, leaf, pinnately-netted 

 veined; B, portion of stem, showing concen- 

 tric layers of wood; C, ground-plan of flower 

 (the parts in 5's) ; D, perspective of flower; 

 E, longitudinal section of seed, showing dico- 

 tyledonous embryo. (From C. Stuart Gager's 

 "Fundamentals of Botany" by permission of 

 P. Blakiston's Son & Co., Publishers.) 



embryo sac in which the egg is formed. The pollen grain produces an 

 outgrowth, or pollen tube, which penetrates the tissues surrounding the 

 egg, and thus the sperm is carried to the egg, fertilizing it. 



Seed plants are commonly divided into 



Monocotyledons ( ). Example, lilies, corn, and 



grasses. (Fig. 123.) 



Dicotyledons ( ). Example, beans and cotton. 



(Fig. 124.) 



The drawings of various stem cross sections will illustrate the dif- 

 ference in the structure of the two types of seed plants. (Fig. 125.) 



Angiosperms. — In this type of plant the ovules are produced in a 

 closed ovary composed of one or more carpels ( ). 



The ovules become seeds, and the carpels and surrounding parts con- 

 stitute a fruit. This fruit may consist of the ripened ovary only, or it 

 may include the calyx ( ) and receptacle also. 



