130 MANUAL OF BOTANY 



internodes of the axis between the whorls of leaves are usually 

 hut little developed, so. that the latter are very closely pressed 

 together. 



The two lower whorls of leaves constitute the perianth, and 

 do not bear sporangia. The other two are sporophylls, and bear 

 microsporangia and megasporangia respectively. 



The most external of the perianth whorls is known as the 

 calyx, and its leaves are called sepals. They are usually green 

 and commonly sessile ; they resemble foliage leaves in their 

 structure and sometimes in appearance ; they are protective in 

 function. 



The second whorl is the corolla, and its leaves are petals. 

 They are generally brightly coloured and delicate in texture. 

 In many cases they are stalked, when the stalk is termed the 

 claw and the blade the limb. 



In some flowers the calyx and corolla are very similar in 

 appearance, being either green or sepaloid, or coloured or 

 petaloid. In a few cases they stand so closely together that it 

 is difficult to see that there are two whorls present. In such 

 cases it is usual in describing the flower not to speak of calyx 

 and corolla, but to make use of the term perianth without 

 distinguishing its constituent whorls. 



The third whorl is made up of the first set of sporophylls, 

 and bears the microsporangia. This whorl is generally called 

 the wndrcecium, and its separate parts are stamens. These 

 leaves are much modified in form, consisting of an upper 

 swoUen portion, the anther, supported upon a somewhat slender 

 stalk or filament. The anther is sometimes sessile, the filainent 

 aiot being developed. Each anther usually contains either two 

 or four piollen-sacs, or microsporangia, in which are developed 

 the microspores or pollen-grains. 



The final whorl, which usiially terminates the axis, is known 

 as the pistil or gijnoecium. The sporophylls of which it is 

 composed are called carpels, and may be distinct from each 

 other or united by their edges to form a solid body. The Butter- 

 cup and the Poppy are instances of these cases respectively. 

 Each carpel, or the body formed by their union, consists of a 

 hollow inferior part, the ovary, and a terminal sticky portion, the 

 stigma. The stigma is sometimes sessile on the ovary, but is 

 generally separated from it by a slender staDj-like portion, the 

 style. The megasporangia or ovules are developed in the in- 

 terior of the ovary, generally arising from a fleshy development 



