THE PHYTOLOGIST. 



No. XXXIV. 



MARCH, MDCCCXLIV. 



Price Is. 



Art. CXC VIU. — Researches in Embryogeny. By W. Wilson, Esq. 



(Continued from p. 735). 



The following is a summary of what has already been published in 

 the ' London Journal of Botany ' for December, and is here added as 

 a necessary sequel to what has already appeared in 'The Phytologist.' 



Since the timp when Dr. Giraud's article on Tropaeolum majus was 

 partially noticed, I have made that plant the subject of close exami- 

 nation ; and the result is that I am compelled to dissent from Dr. Gi- 

 raud's account in several particulars. It is especially objectionable 

 because (contrary to the evident design of the writer) it lends undue 

 countenance to the theory of Schleiden, in the erroneous statement 

 that there exists a traceable mass of " conducting tissue of the style 

 into the carpellary cavity as far as the exostome." In researches like 

 these, it is seldom that the positive statements of other observers can 

 be absolutely disproved ; but here the error admits of demonstration. 

 Dr. Giraud says concerning the " suspensor," that its upper extremity 

 protrudes " through the apex of the nucleus and the micropyle," and 

 that from this extremity a number of cells " hang loosely in the pas- 

 sage leading to the conducting tissue of the style, while the rest unite 

 in forming a process which passes down the outer side of the ovulum 

 within the carpellary cavity." Here we have the position of the 

 supposed passage distinctly marked, as being above the micropyle ; 

 whereas it will be seen that the supposed " loosely hanging cells " 

 must belong to a particular portion of the " suspensor" which never 

 protrudes beyond the micropyle in the manner that it is stated to do. 

 The curious structure and development of this part has escaped the 

 scrutiny no less of Dr. Giraud than of Schleiden and other observers. 

 In the following remarks I shall adopt the term suspensor for the body 

 extending upwards from the embryo, though I am not satisfied that it is 

 quite in accordance with the original views of Mirbel thus to apjjly it. 

 Schleiden, in his attempt to account for the manner in which the sus- 

 pensor gains egress from the coats of the ovulum (for there are really two 

 of these surrounding the nucleus), invents a spurious theorj'-, and gravely 

 asserts that these coats become " obliterated " or undergo " resorp- 

 tion ; " and thus the apex of the suspensor is laid bare ; whereupon 

 it assumes the form represented at fig. 3 ; the part a being directed 



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