284 Examination of the Matured Framework [BOOK n. 



being merely a playing with the unmeaning phrases of the 

 current nature-philosophy, while it revived gross errors like 

 Hedwig's doctrine of the presence of lymphatic vessels in the 

 tissue of the epidermis, and made the Mosses consist of 

 conferva-threads. Phytotomy was on the contrary really 

 enriched by the miscellaneous works of Treviranus published 

 in 1821, especially in respect to questions connected with the 

 epidermis, and by Amici's discovery in 1823, that the inter- 

 cellular spaces in plants contain not sap but air, and that the 

 vessels too chiefly convey air. We may quietly pass over the 

 later writings of Mirbel, Schulze, Link, Turpin and others, which 

 appeared after 1812 and before 1830, as our business is not so 

 much with an account of the literature of the subject as with 

 evidence of real advance. 



Meyen and von Mohl may be said to have commenced their 

 labours with 1830, and in the course of the succeeding ten 

 years they became the chief authorities on phytotomy, though 

 a highly meritorious work of Mirbel's on Marchantia poly- 

 morpha and the formation of pollen in Cucurbita falls as late 

 as 1835. We may even pass over so elaborate a work as the 

 'Physiologie der Gewachse' of Treviranus (1835-1838), which 

 embraces also the whole of phytotomy, because though its 

 treatment of some of the details is good, it presents its subject 

 virtually from the points of view opened before 1812. This 

 work, though it neglects no part of its subject and contains 

 much useful reference to the works of other observers, was 

 unfortunately out of date at the time of its appearance, for 

 owing to von Mohl's labours an entirely new spirit had entered 

 since 1828 into the treatment of phytotomy. 



Though Meyen and von Mohl must be regarded as the chiei 

 representatives of phytotomy from 1830 to 1840, yet they are 

 men of very different importance in the science. The essential 

 difference between them cannot perhaps be better shown than 

 by pointing to the fact, that Meyen's labours cannot at present 

 claim more than a historical interest, while von Mohl's earliest 



