278 Examination of the Matured Frameivork [BOOK if. 



form of elementary organs and the sculpture on their walls 

 more accurately than before. It is true that Link had occa- 

 sionally isolated cells by boiling in 1809, and Treviranus had 

 drawn attention in 1811 to the fact that it was possible to 

 isolate parenchyma-cells in their natural condition ; but neither 

 of them made systematic use of these observations, and to 

 Moldenhawer belongs the exclusive merit of having first 

 isolated vessels and woody cells ; but as usually happens, he 

 did not himself obtain all the possible results from his method 

 of preparation. In his work which indeed embraces the whole 

 of phytotomy, he is continually recurring to one species, maize. 

 This supplies the starting-point in every question to be dis- 

 cussed. The results obtained there are the firm supports on 

 which he leans in the examination of a great variety of plants, 

 which he then compares together at length. This mode of 

 treatment was well chosen both for investigation and instruction 

 in the existing state of the science ; it was a particularly happy 

 idea that of choosing the maize-plant for his purpose ; former 

 phytotomists had generally had recourse to dicotyledonous 

 stems, and preferred those that had compact wood and com- 

 plex rind, but the examination of these plants presents diffi- 

 culties at the present day to a practised observer with a good 

 microscope. Occasionally observers had taken the stem of 

 the gourd, where the large cells and vessels suited small 

 magnifying power, but where many abnormal conditions oc- 

 curred to interfere with their conclusions. The Monocotyle- 

 dons, like the Vascular Cryptogams, had hitherto been 

 comparatively neglected. When then Moldenhawer made a 

 monocotyledonous and rapidly growing plant, with very large- 

 celled tissue and comparatively very simple structure, the 

 chief subject of his investigations, he was sure to succeed 

 in making out many things more clearly than his predecessors. 

 It was an important point that he found the fibrous elementary 

 organs in this plant united with the vessels into bundles, which 

 are separated by a strict line of demarcation from the large- 



