of the existing condition of research; this is one of the reasons why for some time past even official representatives of botanical science often differ so much from one another in their fundamental views on method, and on the question of how much has been actually established and how much still remains doubtful in the main divisions of the subject, that a mutual understanding seems often impossible. That a better state of things in this respect prevails in zoology, physics, and chemistry, is certainly not a little due to the many good compendia and text-books, which endeavour to give some account of the progress of those sciences from year to year. However, during the period from 1850 to 1870 Schacht and Unger attempted to make the results of modern phytotomic investigation accessible to general readers by means of text-books. Such was the nature of Schacht’s[88] work, ‘Die Pflanzenzelle,’ published in 1852, a book which claimed to expound all parts of phytotomy by the aid of the author’s own observations, with occasional reference only to the writings of others; the attempt was so far impossible, as the essential points had already been fully cleared up by the labours of other botanists. The work had however the advantage of attracting the attention of the reader by numerous good original drawings, and the style was enlivened by the constant appeal to original observation; at the same time, through insufficient use of the available literature, the author’s views not unfrequently fell short of the existing standard of knowledge. Worse than this however was a certain defect of education, which led the writer into self-contradiction and to incorrect classification of his facts; things fundamentally important were sometimes neglected for unimportant details, and a certain unreflecting empiricism was apparent in the whole work, in marked contrast with the logical exactness of von Mohl, Nägeli, and Hofmeister. In the second edition of the work, published in 1856 under the title, ‘Lehrbuch der Anatomie und Physiologie der Gewächse,’ we find many improvements in the details, but still on the whole the same formal defects. It is not unimportant in a historical point of view to notice this character of Schacht’s writings, because during this period most young botanists and other persons also derived their knowledge of phytotomy and of the nature of cells chiefly from him; his books did not truly represent the condition of the science; their defective reasoning had an injurious effect on the minds of younger readers, and they introduced into phytotomy and vegetable physiology a habit of accumulating a mass of undigested facts, such as has for some time marked the condition of morphology and systematic botany.