314 PHYLUM XIV. AXTHOPHYTA 



exocarp. Cherry, Peach or Almond flowers and fruits may be 

 Bubstitiited for the Plum. 



(e) Dissect a flower of the Garden Pea (Pisum) so as to show 

 the zygomorphy of the corolla, the ten curved stamens, the 

 single, elongated and several-ovuled pistil. Study developed 

 pods (legumes) and young seeds. Comi)are the zygomorphic, 

 shallow-cupped Pea flower with the related actinomorphic 

 Plum flower. The Sweet Pea (Lathyrus), Bean (Phaseolus), 

 and Locust (Robinia) flowers are similar to those of the Pea. 



(/) Study the flowers and fruits of the Currant or Gooseberry 

 (Ribes), observing their general resemblance to the Apple, but 

 noting the bicarpellary pistil with parietal placentae and the 

 reduced number of stamens. 



ig) Compare the flower of Oenothera with that of Spiraea 

 noting the extreme elongation of the receptacular cup, which 

 adheres to the united, many-seeded carpels; and the reduction 

 of the stamens to two whorls. 



(h) Study macroscopically the mature sporophyte of a 

 Prickly Pear (Opuntia), noting the small, narrow, fleshy, short- 

 lived leaves on the young shoots. In longitudinal and cross- 

 sections of the flowers make out the fleshy cup surrounding the 

 compound ovary, and the many spirally arranged stamens, 

 petals and sepals. Other genera of cactuses show a similar 

 flower structure, and may be substituted for Opuntia, but the 

 plants are mostly wholly leafless. 



(i) Examine macroscopically a staminate flower cluster (cat- 

 kin) of the Walnut (Juglans) or Hickory (Hicoria) noting the 

 crowded, small, many-stamened, apetalous flowers. IMake 

 cross and longitudinal sections of the pistillate flower showing 

 the inferior ovary, surmounted by two large stigmas. Make 

 comparative studies of the fruits and nuts. 



if) Examine the staminate flower clusters of the Oak 

 (Quercus) or Chestnut (Castanea), comparing the several 

 staminate flowers with those of the preceding (i). As the 

 leaves are unfolding, or soon after, find near the tips of the 

 twigs the clusters of two or three pistillate flowers. Dissect 

 these out from their involucres, and note the calyx borne on 

 the edge of the thin receptacular cup which adheres to the tri- 

 carpellary ovary. Examine ripe acorns which are found 

 single seated in the cup-like involucre, or chestnuts which occur 

 several together entirely enclosed in the prickly involucre. 



