BTltUCTURAL BOTANY. 13 



dosed pistil, bnt either attached to the hase of an open 

 pistil (an open scale, as in Pine, or a more evident leaf, as 

 in Cycas), or, in the Yew, encircled at the base by an an- 

 nular disk. The Cycas does not belong to our Flora. 

 The number of cotyledons in Gymnosperms is often more 

 than 2, in Pinus from 3 to 12. The Gymnosperms are 

 represented in the Northern and Middle States by Coni- 

 fers only, of the following genera : Pinus, Abies, La/rix, 

 Thuja, Cupressus, Taxodium,, Junvperus, and Taxus. (See 

 PI.' XIII., 1, 2, 3, and the description of tlie plate.) Gym- 

 twsperm from the Greek -yvfivug, naked, and anepiia, seed. 



46. The Angiospeems have closed jpistils, which con- 

 ceal the ovules in their cavity {Angiosperm, : from Gr. 

 u.yyeXov, a vessel, and ampfia). 



47. The metamorphosing power of the plant is not 

 exhausted by the jx-odnction of a simple axis, but produces 

 also secondary axes. In the lower orders of plants these 

 secondary axes are not much different from the primary 

 axis, but in plants of higher organization the difference is 

 very great. The variety of foims displayed by these 

 plants is astonishing. The primarily cylindrical shape of 

 the leaf undergoes a variety of changes. The simple 

 conico-cylindric axis usually develops leaves; and the 

 leaf appearing first in the lower, then in the upper parts 

 of the axis, and finally at its very top, there imdergoes a 

 series of protean transformations into sepal, petal, stamen, 

 pistil, and fruit. 



The parts of the flower, and so of the fruit, are nothing 

 but whorls of leaves. A tnie simple pistil is a floral leaf, 

 with its edges curved inward and united, forming a closed 

 case, which is the ovary ; and the ovules are borne on what 

 answers to the imited margins of the leaf. Several simple 



