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 results it was established by these facts, that morphological differentiation during growth must not be regarded as an effect of cell-divisions, and from such cases as these the conception of the cell experienced a notable expansion.

Moreover, Nägeli was not satisfied with seeking instructive examples for general morphological axioms in the lower Cryptogams; he devoted special study to the Algae for systematic and descriptive purposes; and his 'Neuen Algensysteme,' which appeared in 1847, and 'Gattungen einzelliger Algen,' of 1849, were the first successful attempts to substitute serious investigation for the mere zeal of the collector in this part of the vegetable kingdom, which had not indeed been hitherto neglected, but had not been systematically worked since the time of Vaucher. In the same spirit Alexander Braun also in his 'Verjüngung' contributed a rich material of new observations on the mode of life of the Algae and the morphological conditions connected with it, and his labours were followed in the succeeding years by the important researches of Thuret, Pringsheim, De Bary, and others, to which we shall recur in a later portion of this history.

But before the examination of the Algae, and soon after of the Fungi also, led to such great results, the systematic botany of the higher plants underwent important changes through the methodical study of the embryology of the Muscineae and Vascular Cryptogams. These groups had been frequently and carefully examined by good observers since the last century, and the systematists, without penetrating deeply into the peculiarities of their organisation, had brought the species and genera, the families and even the higher divisions into tolerable order. Comprehensive and methodically arranged catalogues of these plants had been formed, and attempts had been made to explain their morphology by that of the Phanerogams; Schmidel published valuable observations on the Liverworts