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PHYSIOLOGICAL BOTANY.
of the pith of the recently-developed twigs of the willow(e. g.) this mass assumes a tolerably compact form; intwigs of a year’s growth it is found diffused, and hasformed dotted cells. Now it appears to me, that thismembrane becomes applied whilst in a delicate state tothe wall of the cell, and in certain parts penetrates moredeeply through the secondary deposit, until it reachesthe outermost membrane, and in this manner the appa-rent holes or pits are produced. The prominences seenon the utricle after it has been detached by nitric acid,and which fit into depressions in the membrane of thecell, and the elevations between them, appear to provethis to be the case. The nitric acid probably only actsby contracting the parts and rendering them visible.The membrane inclosing the granular contents, whendetached from the walls of the cell, is only rendered of apale yellow colour by iodine, and at first is not at allcoloured by it. From these considerations, it appearsclear to me that this membrane is applied to the outermembrane of the cells, and that it is again detached fromit by the action of nitric acid, but for this very reason itcannot be a primordial utricle.
Unger’s Memoir in the ‘ Botanisch . Zeit.,’ 1844,s. 498 et seq., upon the Growth of Internodes anato-mically considered, properly belongs here. The authorcounted the internodial cells existing in Campelia Za-nonia, and then compared the number with theirlength and breadth, whence he arrived at the conclu-sion, that the enlargement of the internodes is the resultof the continuous growth of the new elementary parts,and also that the enlargement of the internodes of theaxis arises from both the addition of new elementaryparts and the increase of those already existing. Hethen goes further, and proposes the question of how, andin what manner, the addition of new elementary organs(cells) takes place in the growth of the internodes. Heexamined a longitudinal section which passed throughseveral internodes, and then found that the formation of