LESSON T7.] : 



rgotrfiN:. 



135 



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 he recognized from the 

 pollen alone. 



298. A grain of pbU'en is ma<de up of two coats ; the outer coat 

 thickish, but weak, and fi-equently adorned with lines or bands, or 

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

 birt 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 swell 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 graih 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 ahd three large lobes. The figures niimber from left 

 tb right, beginning at the top. ' - ' ;Jii 



