FERTILIZATION. 123 



153. The student will observe from the above, that in Schlei- 

 den's view of the subject, the pollen tube becomes itself the vessel 

 that contains the embryo, instead of the embryo bein«j formed 

 in the sac of the amnios ; and it will also result from this 

 view, that so far from this impregnation of the embryo sac 

 comin«^ from the pollen tul>c, the pollen tubes become them- 

 selves the subjects of this influence. This reverses entirely 

 the order of tilings as thoy have been considered in all past 

 times. 



Schleiden advances three arguments for the proof of his 

 position, when the tubes cannot be traced unintcrri:ptedly from 

 stiffma into the cmbrvo snc. In some cases, the cellular 

 .... ^tance of the nucleus is so firm and opaque through 

 which the tubes pass, that the tubes cannot be traced through 

 it; but the indentity of the embryo with the pollen tube, he 

 infers. 1. From the constantly equal diameter of the latter 

 exterior to the embryo sac, and of the former just within it. 

 2. The invariable chemical similarity of their contents, shown 

 by the reaction produced by the application of water, oil of 

 sweet almonds, iodine, sulphuric acid and alkalis. 3. In 

 '■ -^li plants as bear several embryos, there is always precisely 

 same number of polk n tubes. 



154. The analogy drawn from the animal kingdom, as applied 

 to the fcitann-ns and p'.stils, has long aj>poared to us a useless 

 and incorrect one, and we have lonor since ceased to make allu- 

 sions of this kind in our lectures on this subject. The pro- 

 duction of spores in cryptogamic plants, and of buds or germi- 

 nating points, in all |)lants ; it seems to us that no such a|)pa- 

 ratus is needed, and a strong presumption that no ?uch exists. 



It seems to us much more simple, and the supposition leaves 

 the vegetable kingdom unencumbered with ideas drawn from 

 a department of nature from which it difters so greatly, and 

 which tends to lead to error, to suppose that the geim of the 

 future plant is |)roduced in the stamen, and the development 

 of the pistil aflords it a ()lace of deposit and nourishment. 



15.J. SonK} dilferent contrivances from those already mention- 

 ed for etfocling tin? entrance of the pollen tubes into the foramen 

 of the ovule, should ntt be omitted in this place. This object is 

 etfected in the fullowin^: manner, in the Armeria vulraris and 

 Statice, as described in the Library of Useful Knowledge, 

 \rticle Botany, p. 110. 



L'.'t the ellipse a a, tig. 14.'>, A. rr present a section of an ovary 



of this plant. From its base there arises an umbilical cord, 



ff, which curves after reaching about half the length of the 



cavity, and bending down upon itself again, turns partially 



