Position of the Stigma and Placenta in Plants. 35 



having a cavity of about an inch at the back of the shelves (two 

 cross bars might prevent the plant-holding papers from being pushed 

 too far back) with a lid at the top, and sliding in one or more 

 frames supporting Welsh Plane well dosed with the chloride and 

 dried ; gun-wadding prepared might perhaps do as well, but I have 

 not at present tried either material. A servant might occasionally 

 take out, dry, and replace the slides without having access to the 

 plants. 



One unconnected remark and I have finished : my vasculum is 

 provided with a canvass lining, which I take care to have well-wetted 

 in warm weather, to supply much of that moisture that would other- 

 wise diffuse into the air from the contained plants alone. It is 

 further provided with a covering of canvass to be used only in hot 

 sunshine when it is wetted to keep the box cool by evaporation from 

 its surface. 



Woodloes, near Warwick, November 1842. 



XL — On the relative position of the Divisions of Stigma and 

 Parietal Placentae in the Compound Ovarium of Plants. By 

 Robert Brown, F.R. & L.S * 



To estimate correctly the importance of the relation between 

 the divisions of the Stigma and the parietal placentae of the 

 compound ovarium, namely, whether when agreeing in num- 

 ber they are placed opposite to or alternate with each other, 

 it is necessary to take into consideration the theoretical view 

 which appears the most probable of the origin or formation of 

 a simple ovarium, and that of the stigma belonging to it, as 

 well as the various kinds and degrees of confluence by which 

 the real nature of both organs, but especially the latter, is so 

 often obscured. 



It is at present, I believe, universally agreed to consider a 

 polyspermous legumen as that state of the simple ovarium, 

 which best exemplifies the hypothetical view of the formation 

 of this organ generally adopted ; namely, that it consists of the 

 modification of a leaf folded inwards and united by its mar- 

 gins, which in most cases are the only parts of the organ pro- 

 ducing ovula ; or, at least, where this power of production is 

 not absolutely confined to the margins, it generally commences 

 with or includes them. 



The exceptions to the structure as here stated are of two 

 kinds : — 



First. Where the whole internal surface of the carpel is 



* This article, which is referred to at p. 255 of No. 65, is extracted from 

 Mr. Brown's account of Cyrtandrea, given in the second part of Dr. Hors- 

 field's ' Plantae Javanicse Rariores,' published in 1840. Separate copies of 

 this article were distributed in December, 1839. 



D2 



