336* Linnean Society. [June 20, 



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 Balanophorece, however, he reserves 

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

 to lay before the Society. 



