Exercise XV 



ORGANIZATION OF HIGHER PLANTS 79 



Flower and fruit 



Each pair of students will be provided with a 

 flower (probably a tulip). Study the following 

 structures, progressing from the outside inward. 

 The pericanth consists of an outer series of green 

 leaves (sepals), not always present, and colored, 

 modified leaves (petals). The inner sex organs 

 are called stamens (male) and pistils (female). A 

 "perfect" flower has both stamens and pistils. 

 Each stamen consists of a slender stalk at the 

 end of which is the anther, which produces the 

 pollen grains. Examine some pollen under the 

 microscope. Recall that this represents the male 

 gametophyte. 



The pistil consists of an enlarged basal portion, 

 the ovary, which supports a slender tube, the 



style. The tip of the style is slightly flattened, 

 forming the stigma. When the flower is receptive 

 to fertilization, the stigma becomes sticky, help- 

 ing it to retain the pollen grains. Inside the ovary 

 are several ovules, which produce the female 

 gametophytes. (Read carefully the discussion of 

 the formation of the egg and pollen, and fertiliza- 

 tion in Weisz, pp. 556-559; S. P. T., pp. 368- 

 378; Villee, pp. 182-184.) 



After fertilization and formation of the em- 

 bryo, the ovule tissues harden, forming a seed 

 coat. In some plants, the seeds are retained in 

 the ovary, which develops into a fruit. Examine 

 either an apple or pear, cut in cross sections. 

 Identify as many structures as you can. After 

 that, it's yours! 



EQUIPMENT 



Per student 



compound microscope 



porcelain spot plate 



slides and cover slips 



The following prepared slides: 



stem of Medicage (alfalfa) 



stem of Zea mays (corn) 



2- to 4-year old woody stem of Liriodendron (tulip 



tree) 



tangential section of Liriodendron 



radial section of Thuja (arborvitae) 



leaf of Liqustrum (privet) 



root tip of Zea mays 



root of Ranunculus (buttercup) 



Per 2 students 



medium-size funnel 



capillary tubing (about 3 ft) or 0. 1 ml calibrated pipet 



T-tube 



punch cock and screw clamp 



2 ring stands with 4 clamps 



rubber tubing 



400-ml beaker 



geranium plant 



tulip or other flower 



apple or pear 



Per 8 students 



graded sucrose solutions (0.1 to 0.5 M) (20 ml) 



vaseline 



flexible wire for joints 



red onion 



Per laboratory 



assorted pieces of polished wood 



wall charts of stem, leaf, and root anatomy 



