STRUCTURAL BOTANY. 13 



closed pistil, but eitlier aitac/ied to the hase of an open 

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

 in Cycas), or, in the Yew, encircled at the base bj 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 ^"orthern and Middle States by Coni- 

 fers only, of the following genera : Pinus, Ahies, Xarix, 

 Thuja, Ciipressiis, Taxodiurn, Juniperus, and Taxus, (See 

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

 nosperm from the Greek Yvnv6g, naked, and cnepfia, seed. 



46, The AxGiosPEEMs have closed pistils, which con- 

 ceal the ovules in their cavity {Amjiosperm : from Gr. 

 dyyeiovy a vessel, and airepiia). 



47. The metamorphosing power of the plant is not 

 exhausted by the j^oduction 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 forms 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 undergoes 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 true 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 united margins of the leaf. Several simple 



