IMPERFECT FLOWERS. 61 
ber, two long and two short. TZetradyn’amous stamens are 
six in number, four long and two short (as in the Mustard 
tribe, Fig. 182). Again, hypégynous stamens may be seen 
in the Crowfoot tribe and in Fig. 132; and perigynous sta- 
mens in the Rose tribe and Fig. 133. What is the differ- 
ence? You need not be told the meaning of these words 
(§§. 83, 84). 
109. Some plants have their essential organs separated, so 
that the stamens are all found in one sort of flowers, the 
sterile, and the pistils are all in another sort, the fertile. So 
Fig. 186. Flower of Lizard-tail (Saurwrus); it is perfect, but naked, 7. ¢., with no 
floral envelopes; stamens seven, pistils three. 
Fig. 187. Flower of Ash (Fraxcinus),—naked, with two stamens and one pistil. 
Fig. 188. Staminate flower of Willow,—made up of two stamens and a bract. 
Fig.189. Pistillate flower of the same,—merely one pistil and a bract. 
it is in the Begonias (Fig. 185), and in the Willows (Figs. 188, 
189). All such flowers are called cmperfect, and only the fer- 
tile bear fruit. 
110. A perfect flower is one that has both stamens and 
108. In what two cases do we mark the length of stamens? Define “sta- 
mens didynamous ;” “stamens tetradynamous ;” “stamens hypogynous ;” 
“stamens perigynous.” 
109, What do you understand by “sterile flowers?” by “ fertile flowers ?” 
110. What is a perfect flower? complete? imperfect ? 
