162 Dr. Giraud's Contributions to Vegetable Embryology. 



dowinents of the sexual organs of plants, and of the offices which the two sets 

 of generative organs respectively perform. 



With the hope of removing some of the uncertainties which are still attached 

 to this litigated question, and of gaining some determinate information on yet 

 unsettled points, I have attempted a series of observations on the mode of de- 

 velopment of the embryo in Tropceolum majus, the results of which will, I 

 trust, contribute in some degree to furnish materials for a theory of phanero- 

 gamic reproduction. 



The extreme simplicity of the ovarium of the Tropceolece, and the com- 

 paratively large size of their solitary ovules, render the individuals of this 

 family peculiarly fitted for the kind of observations herein detailed ; and in 

 these respects their allies, the Geraniaceee, are similarly circumstanced. 

 The following are the essential characters of the so-called female organs of 

 Tropceolum majus: "Ovary 1, 3-cornered, made up of 3 carpels; style 1; 

 stigmas 3, acute ; ovules solitary, pendulous ; fruit indehiscent, separable into 

 three pieces from a common axis ; seeds large, without albumen, filling the 

 cavity in which they lie ; embryo large ; cotyledons 2, straight, thick, consoli- 

 dated together into a single body ; radicle lying within projections of the co- 

 tyledons." 



The following observations are arranged under seven general heads, corre- 

 sponding with as many progressive periods in the growth of the so-called fe- 

 male organs, extending from the completion of the anatropous development of 

 the ovule, to the perfect formation of the embryo ; or from the commence- 

 ment of the expansion of the bud, to the complete formation of the fruit*. 



First Period. — On making a section of a carpel (just before the expansion 

 of the bud), from its dorsum inwards towards the axis of the pistil, and in the 

 direction of that axis, the solitary ovule is at the same time divided, and is 

 found to have completed its anatropous development (Tab. XVI. fig. 1.). Con- 

 tinuous with that part of the columella which forms the placenta, is a portion 

 of rather firm and dense cellular tissue, inclosing a bundle of vessels, and 

 forming the so-called umbilicus : this, with the vessels it incloses, descends in 

 apposition with the placenta to form the raphe (fig. I, a.): and, near the point 

 where it terminates in the base of the ovule, the vessels are gradually lost, or 

 rather terminate in closed extremities. The nucleus has only one tegunientary 



* The results, as here detailed, are collected from a great number of dissections^ 



