812 Botanical Society of Edinburgh : — 



valence in Conifer ce having been anywhere noted. In Podocarpus 

 dacrydioideSy the species selected for illustration, the roots and root- 

 lets are studded at intervals with spherical bodies, of diameters 

 varying between the ^^th and ^th of an inch, either attached by 

 a very short pedicel, or absolutely sessile, and sometimes even sunk 

 into the bark of the root. They are easily detached, leaving a small 

 scar, are of a soft and spongy consistence, smooth and even on the 

 surface, of a pale reddish colour, and in a vertical section are seen 

 to be composed of — (1) a mass of spongy cellular tissue, aggregated 

 round (2) a central vascular axis, which extends from the wood of 

 the root to the centre of the sphere, and (3) a delicate cuticle. 

 Each of these tissues is described in detail, and illustrative figures 

 of the exostoses of P. dacrydioides and of their microscopic anatomy 

 accompany the paper. With regard to the exostoses of the roots of 

 other plants. Dr. Hooker observes that for the most part their struc- 

 ture is approximately the same as those of the Podocarpus, but they 

 are very much larger in most herbaceous plants than in the arboreous, 

 are more irregular in form, and are destitute of the vascular axis. 

 In some species they are perennial, in others annual. In the Labur- 

 num they form fleshy branched masses, as large as the fist, and are 

 full of vascular tissue. Morphologically, he looks upon them as 

 transformed root-fibrils, but regards their special function as obscure, 

 although they may be supposed to be subservient to the office of 

 selection of nutriment. In conclusion, he indicates a remarkable 

 morphological analogy between them and the tubers of the root- 

 parasite Balanophora, which are supplied with an abundant develop- 

 ment of vascular tissue, mainly derived from the vascular axis of the 

 roots upon which the Balanophora are parasitical. In this case. 

 Dr. Hooker thinks there can be no doubt that the parasite exerts a 

 specific or diseased action in the root-stock, which results in the 

 development of a vascular bundle analogous to a rootlet, which is 

 prolonged into the tuber of the parasite, and which afterwards in- 

 creases greatly, branches, and resembles in its appearance as well as 

 in its relation to the root-stock, the vascular branches occupying the 

 axis of the branched exostoses of the Laburnum. On the subject of 

 the development of the tissues of Balanophoreae, however, he reserves 

 further details for a monograph of that Order which he is preparing 

 to lay before the Society. 



BOTANICAL SOCIETY OF EDINBURGH. 



February 8, 1855. — Professor Balfour, President, in the Chair. 



Mr. T. Kirk, of Coventry, sent for exhibition a specimen of Ce- 

 rastium triviale, with the carpellary leaves partially turned inwards, 

 so as to show distinct parietal dissepiments. The placentas were 

 free and central. A very similar specimen is figured and described 

 in the 'Gardener's Chronicle' (1844, p. 557), and ' Lindl. Veg. 

 Kingdom' (p. 497). 



