PROBLEM 3. How Co?nplex Flants 



seeds are formed. Finally, they dis- 

 covered that reproduction in seed plants 

 is in many respects like reproduction in 

 complex animals. The embryo you found 

 in the seed grows from a fertilized egg- 

 cell which is formed by the union of 

 two dissimilar gametes. The gametes, as 

 in animals, are sperms and eggs. But be- 

 yond this we must not expect to find 

 much similarity since plants and animals 

 are so different in structure. The plant 

 does not hav^e organs corresponding ex- 

 actly to the spermaries and ovaries of an 

 animal. Where are the sperms and eggs 

 produced in plants? To answer this we 

 must examine the blossom or flower. 



The flower. Let us find out how a 

 flower is constructed so that we may 

 find the gametes and learn how the seeds 

 are made. Tulips, lilies, or sweet peas are 



Reproduce 439 



large and easy to study. See Exercise 3. 

 The tulip has six brightly colored or 

 white leaflike parts. They are arranged 

 in an outer circle and an inner circle, 

 each consisting of three parts. In many 

 flowers the outer circle (calyx) is green 

 and the parts are known as sepals. The 

 inner circle (corolla) consists of bright 

 petals which often are larger than the 

 sepals. Inside the floral envelope is a circle 

 of stamens (stay'mens). Each stamen 

 consists of a threadlike part with a knob 

 on the free end. In the very center of the 

 blossom is a single pistil. The number, 

 shape, size, and color of all flower parts 

 are different in different kinds of plants. 

 Often it is these differences which are 

 used in classifying the plant. 



Flower parts used in reproduction. It is 

 the stamens and pistils that are used in 



Stamen^ 



Pistil 



Ovary l|^ 

 Anther (enlarged) (enlarged) f-J^ 



Fig. 387 The flower parts of a lily. Two of 

 the leaflike parts have been cut away. How 

 ■many of each of the flower parts were there? 

 Study the sta?nen and tl.ie pistil. 



Fig. 387a X-ray of a lily. Petals and sepals are 

 similar a7id attached to each other. There are 

 six stamens, although the photograph seems to 

 show three, (general electric; x-ray corp.) 



