50 FAMILIAR LESSOXS IN BOTANY. 



ness; the crape myrtle has light-brown, egg-shaped grains; 

 the mallow has a white opaque sphere, covered with elon- 

 gated projections (papillae), and looks just like an infinites- 

 imally small gherkin. The crimson Texas-star {Sahbatia 

 hracMata) has golden-colored grains shaped like rice. These 

 forms are as fixed and uniform as any other peculiar char- 

 acteristic distinguishing one family of flowers from another. 



112. The microscope shows us also that these grains con- 

 sist of a delicate tube of great tenuity, surrounded by a 

 thin liquid, which is inclosed in a thin sack or skin. 

 When the pollen falls upon the stigmatic surface of the 

 pistil, this sack bursts and the pollen tube issues there- 

 from, penetrating the stigma, descends the hollow tube of 

 the style, and finally reaches and fertilizes the ovules in the 

 germ below. As insignificant as this dust may appear to 

 you, it is just as important as the root, the stem, or the 

 leaf If for a few years the corn and wheat blossoms should 

 fail to perfect pollen, starvation to millions would be the 

 consequence. Eeproduction depends on this, and no seed 

 can mature without it. 



113. Observation will teach you that the stamens are 

 sometimes helow the pistil, sometimes around it, and again 

 iqyon it. "When they arise from the cal3^x, they are said to 

 be^;e;-/p^j/;i02^5; from the pistil, ejngynous ; under the pistil, 

 hypogynons. When the stamens are longer than the co- 

 rolla's depth, so that they project beyond, as in the honey- 

 suckle, they are said to be exserted (Latin, exserere, to 

 stretch out) ; when shorter than the corolla, included 

 (Latin, includere, to shut up, to confine within). When 

 they bend down in a curve, they are said to be declinate 

 (Latin, declinare, to lean, to bend). 



112. What does the pollen grain consist of ? When it falls on the stigma, what 

 takes place ? What if the pollen of grain-bearing plants should all fail for years 

 to perfect their pollen ? 



113. When the stamens rise out of the calyx, what are they called? When 

 npon the pistil ? Under the pistil ? When longer than the corolla ? When 

 shorter ? When they bend downward ? 



