464 Miscellaneous. 



These diversities of venation would have appeared much more ex- 

 traordinary a few years ago, before the modern observations upon 

 the formation of the tissues of the leaf. It was then usual to speak 

 of the veins as the framework of the leaves, which implied, more or 

 less positively, the idea that they preceded the parenchyma, and that 

 this was formed around them as about a solid point of support. We 

 now know that every organ commences by being cellular and of 

 slight consistence, and that the projecting parts precede the veins. 

 Hence the woody tissues and the bones of organisms are only a con- 

 sequence of the soft parts. It is, however, singular that in very 

 nearly allied plants, and sometimes in two portions of the same leaf, 

 the solid parts should sometimes occur in the middle of the lobes and 

 sometimes outside of them ; and it appears probable that at the 

 actual moment of formation of the veins they would present a more 

 constant position. Observations on the formation of leaves, and 

 especially on the development of the veins, are not yet sufficiently 

 numerous to lead to any conclusion upon this point. But probably 

 it will be found that the exceptional veins, or those which run 

 towards the lateral sinuses of the leaf, are veins which have deviated 

 at a certain epoch, or veins which originally corresponded to a pro- 

 jection the termination of which has been arrested in its develop- 

 ment, whilst the parts originally depressed have increased in size. — 

 Bibl. Univ., Archives des Sciences, Oct. 1864, p. 164. 



On the Development of the Flowers of the Corapositee. 

 By Professor Wolfgang. 



The course of development, which may be observed particularly 

 well in the common Sowthistle (Sonchus arvensis), is described by 

 the author as follows : — " The flowers of the capitulum are developed 

 after the leaves of the involucrum, in a direction from the periphery of 

 the receptacle to its centre. The first traces of leaves appear in the 

 form of oblique prominences, directly continuous with the epithelium 

 of the receptacle. The future point of the flower by no means cor- 

 responds with the point of this prominence. Subsequently these com- 

 mencements of flowers become perfectly hemispherical ; the organic 

 point of the bud remains behind in its growth, whilst around the 

 apex there is formed a circular elevation, which in a short time forms 

 a sort of crater. On the outside, a little above this annular rampart, 

 there appear sometimes some cushion-like inflations, perhaps the 

 commencement of the obliterated calyx. There is no trace of the 

 pappus. Subsequently the five petals originate on the margins of 

 the crater- wall ; their increase takes place at the base, and they curve 

 inwards successively in a geniculate form. The anthers follow 

 these, alternating with them ; they are developed on the inner slope 

 of the crater. The petals become soldered together from the base 

 up to the place where the lobes afterwards make their appearance. 

 The pappus projects from the outer wall of the crater-margin, but 

 not until the anthers have advanced considerably in their development : 

 from its origin and its nature, it must be regarded as an accessory 



