Dr. Balfour on Megacarpsea polyandra. 75 



forms over the earth, both in the present period and in past geological 

 times, has shown that in all soils in -which plants grow, Diatoms are 

 present, often in considerable quantity, and in great variety. He 

 ascribes to them a great part in the formation of such soils, and it is 

 probable that by their life and growth they extract much silica from 

 the water in which they hve, and transfer it at their death to the soil. 

 The sediment of all rivers contains a considerable amount of Diatoms, 

 as, for example, the mud of the NUe and that of the Ganges, which 

 have formed the great Deltas of Egypt and Bengal. 



2. " Remarks on specimens of MeyacarpcBU polyandra, Bentham," 

 by Dr. Balfour. 



' The interest of the plant consists in its possessing a number of 

 stamens (from 12 to 15), quite abnormal in the order of Cruciferse, 

 to which it otherwise belongs ; and which might seem, taken alone, 

 to place it between that order and Papaveracese ; but when these 

 extra stamens are viewed as developments of the glands which are 

 present in the Cruciferee on the disk or torus, between the petals and 

 the ovary and ordinary stamens, the plant may well be referred to 

 that order. 



The genus Megacarpcea was first discovered, I believe, by Fischer, 

 in the salt steppes and calcareous hills of Turkistan, in the neigh- 

 bourhood of the Caspian Sea ; and by Ledcbour in Siberia ; and was 

 originally referred to Biscutella. Two species are described by 

 DeCandoUe (Prod. i. 183), but so imperfectly, that till further in- 

 formation is obtained, it is impossible to determine whether the plant 

 before us, from the Himalaya, is identical with either of them, 

 especially M. laciniata from the xVltai Mountains, or a new species 

 which is to bear the name of M. polyandra. 



Megacarpcea (probably this very species) was next met with by 

 Dr. Hugh Falconer in the Highlands of Little Tibet, on the Husora 

 River, an affluent of the Indus, and in the same country by the late 

 Mr. J. E. Winterbottom, who described it to me as growing to 8 feet 

 high on the Barzil Pass, upper glen of the Kishenganga River, between 

 Kashmere and xAstor ; but neither of these botanists was, I believe, 

 so fortunate as to obtain the flowers, which were first seen by Capt. R. 

 Strachey in 1848, on a visit to the glacier sources of the Pindar 

 River iri Kumaon, up to which date the existence of the plant in the 

 British Himalaya was unknown ; nor has it been discovered, so far 

 as I am aware, in any other of our provinces — at least those south of 

 the Sutlej River. Here it occurs in three locahties, where the 

 climate resembles or approximates to that of Little Tibet, Turkistan, 

 and the other habitnts, viz. extreme cold in winter, and extreme heat 

 and aridity in summer, conditions wliich have proved favourable to 

 the migration or presence of many other Tibetan and Siberian plants 

 on the dry northern slope of the Himalayan range, where a system of 

 vegetation is established in marked contrast with what prevails on the 

 Indian face, which is annually for three months deluged with rain*. 



* A very instructive example of the manner in which plants are distri- 

 buted in distant regions of similar physical character is afforded by Calli-. 



