ANTHOPHTTA. 261 



but too frequent a recurrence of this is guarded against by 

 various structural devices. 



496. The foregoing are but a few of the general modifi- 

 cations which flowers have for securing proper pollination ; 

 they must serve to direct the student's attention to this 

 interesting part of the study of plants, which can be taken 

 up in connection with the writings of Darwin, Miiller, 

 Gray, anS others. 



Practical Studies. — {a) Collect a few wild buttercup flowers. Be- 

 gin at the lower side of the flower and carefully remove the five 

 green sepals constituting the so-called calyx, next the five yellow 

 petals constituting the so-called corolla, next the many stamens, and 

 last the numerous small pistils which cover the rounded end of the 

 floral stem. Make a careful drawing of a representative of each 

 part. 



(6) Mount in water (after moistening with alcohol) a little of the 

 pollen of the morning-glory, sunflower, mallow, and Indian corn. 

 Note the surface markings. Crush the cells and test with iodine. 

 Pollen-grains may be germinated by placing them in a five-per-cent 

 solution of common sugar in water: The pollen-tubes may also be 

 found by carefully mounting stigmas or longitudinal sections of stig- 

 mas. Many grasses are good subjects for such studies. 



(c) Remove the pistil from a fresh pea-flower. Split it longitudi- 

 nally, and observe that the ovules are in a row along one seam (su- 

 ture). Make many cross-sections of another pistil, so as to secure 

 sections of ovules, in which note the ovule-body and the coats. Make 

 cross-sections of younger and younger unopened flowers of the pea, 

 and study the development of the ovary and ovules. It is very eAsy 

 to get specimens showing the ovary not yet closed, and the ovules as 

 very small outgrowths from its margins. 



(d) Make longitudinal sections of several young pea-pods in such 

 manner as to secure thin sections of the ovules. By selecting pods 

 of different ages, the large embryo sac, with the young embryo in 

 various stages of growth, may be observed. 



(e) Carefully dissect and examine a pea after soaking over night in 

 water. Note the short curved stem, tipped by a root, the two thick, 

 starch-gorged leaves (cotyledons) with smaller leaves between them. 

 Examine in like manner a bean, seeds of the apple, squash, buck- 

 wheat, oat, Indian corn. Note the endosperm when present. 



(/) Examine in succession ripened fruits as follows : 1, marsh- 



