Observations on the Organogeny of the Flower. 405 



" Several eminent botanists have been engaged for some years 

 in the investigation of plants with a free central placenta, or in 

 which the part which bears the ovules occupies the centre of the 

 cavity of the ovary, without lateral attachments to its walls. 

 Nevertheless this important question is not yet sufficiently set- 

 tled; perhaps even, as M. Duchartre proceeds to prove, a wrong 

 view of it is generally taken. This skilful botanist recollected 

 that there was a safe means of deciding it in a positive manner, 

 and that this means consisted, not in making multiplied observa- 

 tions on nearly full-grown flowers, as had most frequently been 

 done, but in going back to the first origin of the parts, and fol- 

 lowing them in their formation and development; in a word, 

 studying their organogeny. 



" In fact, the advantage of this kind of research is easily under- 

 stood, and what M. Schleiden says on the subject of the pistil 

 may be applied to all the important parts of plants : l The 

 history of the development should be the sole guide, and it will 

 conduct to a perfectly safe conclusion as soon as ever it is well 

 understood in its generality/ 



" One of the most remarkable investigations that have been 

 made on free central placentas is that of M. A. de St. Hilaire. 

 In this excellent memoir there occurs the following passage : ' If 

 the placentas I have just described be observed before fecunda- 

 tion, it will be found that they are surmounted by a pretty firm 

 filament, rather transparent, of a yellowish green colour, which 

 penetrates the interior of the style ; but, after the emission of the 

 pollen, the ovules, beginning to increase in size, crowd round the 

 filament, it breaks, and it is then only that the placenta becomes 

 really free. The ovules, continuing to grow, cover the place 

 which the filament occupied, and soon no vestige of it can be 

 discovered/ 



" The opinion of M. A. de St. Hilaire has been adopted by most 

 botanists. Thus M. Endlicher, in the enumeration of the cha- 

 racters of the family Primulacece, says : c Placenta basilari globosa, 

 sessili vel substipitata, rarius columnari, primum fills arachno'ideis 

 cum vertice ovari cokcerente, mox libera, 3 Thus again, in the 

 volume of the ' Prodromus * which has just appeared, M. Duby 

 assigns a like character to the placenta of this same family: 'Pla- 

 centa centrali globosa, apice filo cum interna styli substantia con- 

 tinua, mox libera. 3 



"By these citations it is seen, that in the most important 

 works the central placenta of Primulacecs is described as being at 

 first attached by its superior extremity to the summit of the ovary 

 or to the style, and only becoming really free at a later period 

 and by the rupture of its threads of communication. 



" The author opposes this opinion, as well as that of Dr.Lindley, 

 which appears to relate the organization of the placentas of Pri- 



