PEANSBO&AMIA. 



237 



productive organs are in one flower, when the ovaries are 

 highest on the stem, the stamens being next, and the sterile 

 leaves (if any) lowest of all (Pig. 127). There is, more- 

 over, great diversity in the development of the sterile 

 leaves, varying from a few small green or pale leaves to 

 two or more distinct whorls of sepals (the outer) and petals 

 (the inner) which may show great differences in size, shape, 

 texture, and color. 



481. The stamens of Angiosperms often bear so little 

 resemblance to leaves that their real nature would not be 



Fio. 128.— Pollen-cells with roughened walls. 

 Mallow (Lavatera). Highly magnified. 



A, of Chicory; B, of Flowering 



suspected. There is usually a slender stalk, the filament, 

 at the top of which are from one to four pollen-sacs, the 

 latter forming the anther. We may regard the filament 

 and its extension (the so-called connective) between the 

 pollen-sacs as representing a very narrow leaf upon which 

 the pollen- sacs develop as outgrowths. Sometimes the 

 stamen is broad, showing at once its leafy nature. 



482. The development of the pollen-cells is like that of 

 the spores of Fern worts and the pollen of Gymnosperms. 

 Certain internal cells (called pollen mother-cells) in the 



