PHANEBOGAMIA. 337 



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

 ovules, in which note the ovule-body and the coats. Maljc 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-mari- 

 gold (follicle) ; 2, pea (legume); 3, mustard (capsule); 4, parsnip (cre- 

 mocarp); 5, oak (nut); 6, sunflower (achene); 7, Indian corn (cary- 

 opsis); 8, melon or cucumber (pepo); 9, gooseberry (berry); 10, cherry 

 (drupe); 11, apple (pome). Numbers 6 and 7, which are popularly 

 called seeds, are composed of a large seed enclosed in a tightly fitting 

 ovary-wall. 



(g) Study the Indian corn as an example of a wind-pollinated (ane- 

 mophilous) plant. Note the position of starainate (in the tassel) and 

 pistillate (in the ear) flowers. Estimate the relative number of pollen- 

 cells, and ovules (one in each ovary). 



(Ji) Study the position of the nectar in clover (at the bottom of the 

 corolla), columbine (in deep sacs of the petals), and buttercup (on 

 glands at the base of the petals). 



(i) Examine flowers from several different plants of eyebrights 

 (Houstonia), puccoon (Lithospermum), and cultivated primrose. Ob- 

 serve that on some plants the flowers have long stamens and short 

 styles, while in others they are the reverse. By measurements the 

 anthers of the one form will be found to have exactly the height of 

 the stigmas of the other. Many other flowers show this dimorphism ; 

 a few show trimorphism, i.e., three forms. 



(J) Observe the flowering of spring-beauty (Claytohia), and notice 

 that the stamens mature before the stigmas are ready for pollination. 

 Observe in like manner thistles and sunflowers in which proterandry, 

 as it is called, takes place also. Now observe the flowering of the 

 strawberry and the apple, in which the pistils mature before the 

 stamens. This is known as proterogyny. Both proterandry and 

 proterogyny are included under the general term of dichogamy. 



