LESSON 17.] 



POLiEN. 



115 



Under the microscope it is found to consist of grains, usually round or 

 oval, and all alike in the same species, but very different in different 

 plants. So that the plant may sometimes be recognized from the 

 pollen alone. 



293. A grain of pollen is made up of two coats ; the outer coat 

 thickish, but weak, and frequently adorned with lines or bands, or 

 studded with points ; the inner coat is extremely thin and delicate, 

 but extensible, and its cavity is filled with a thickish fluid, often 

 rendered turbid by an immense number of minute grains that float 

 in it. When wet, the grains absorb the water and sweE so much 

 that many kinds soon burst and discharge their contents. 



299. Figures 241 - 250 represent some common sorts of pollen, 

 magnified one or two hundred diameters, viz.: — A pollen-grain of 

 the Musk Plant, spirally grooved. One of Sicyos, or One-seeded 

 Cucumber, beset with bristly points and marked by smooth bands. 

 One of the Wild Balsam-Apple (Echinocystis), grooved lengthwise. 

 One of Hibiscus or Rose-Mallow, studded with prickly points. One 

 of Succory, many-sided, and dotted with fine points. A grain of the 

 curious compound pollen of Pine. One from the Lily, smooth and 

 oval. One from Enchanter's Nightshade, with three small lobes on 

 the angles. Pollen of Kalmia, composed of four grains united, as in 

 all the Heath family. A grain from an Evening Primrose, with a 

 central body and three large lobes. The figures number from left 

 to right, beginning at the top. 



