386 DEVELOPMENT OF PLACENTA. [BOOK i. 



of vegetation, as it were a priori, without adducing in support 

 of it a single example taken from the observation of nature. 



' ' To my no small satisfaction, I became, from day to day, 

 more and more convinced, both from my own analyses and 

 those of other accurate observers, of the correctness of 

 Agardh's views ; and, moreover, I saw that all those appear- 

 ances which speak the most in favour of De Candolle's 

 theory, can also, without effort or violence, be demonstrated 

 according to the principles laid down by Agardh : for example, 

 the apparent arrangement of the seeds on the two margins of 

 the carpellary leaf at the opening of the pod of Leguminosse, 

 the frequent recurrence of an even number of ovules in simple 

 polyspermous carpels, or in each cell of compound fruits, &c. ; 

 and that on the other hand all those appearances which 

 after De Candolle's ideas can with difficulty, or as he himself 

 admits, cannot at all be explained : for example, the attach- 

 ment of the seeds in the fruit of Crucifers, the structure of 

 Borageworts, Ochnads,Labiates, &c., become under Agardh 1 s 

 theory examples of the explanation of the appearance of the 

 fruit of other natural families in the simplest and most satis- 

 factory manner." 



Duchartre has proved the truth of this theory by direct 

 observation of development : " At its first appearance the 

 flower of the Primworts shows itself in the form of a small 

 globule, a little depressed, and entirely cellular. In this 

 state it is embraced by the young bract, the axil of which it 

 occupies. Very soon, towards the base of the nascent bud, a 

 slight peripherical and continuous swelling is seen, the free 

 border of which is speedily crimpled into five little festoons. 

 This swelling is the nascent calyx, and the five little processes 

 the five organic sepals already soldered together. While the 

 calycmal protuberance is making its appearance the young 

 bud becomes a little enlarged, and five small rounded papillae, 

 alternating with the five sepals, are soon to be distinguished 

 upon the upper part, now surrounded by the calyx. In a 

 short time these papillae become elevated, disengaged from the 

 common base, and are to be distinguished as five small pro- 

 jecting bodies, rounded at the summit and sides, and slightly 

 compressed within and without. These are easily recognised 



