266 Examination of the Matured Framework [BOOKII. 



but he did not give a decided answer to the question. He 

 declared however distinctly against Hedwig's reconducting 

 vessels in the epidermis, as Sprengel had done, and it is worthy 

 of recognition that he understood the true nature of the corners 

 where three longitudinal walls of the parenchyma meet, while 

 later observers found difficulties in them. 



Before the appearance of Bernhardi's work the Royal scien- 

 tific Society of Gottingen proposed a subject for a prize in the 

 year 1804, which shows very plainly what uncertainty was felt 

 at that time on all points of phytotomy. For this reason it 

 will be well to give it at length from the preface to Rudolphi's 

 1 Anatomie der Pflanzen ' (1807) : 'Since some modern physiolo- 

 gists deny the peculiar construction of vessels in plants which 

 is attributed to them by other and especially the older 

 observers, it would be well to institute new microscopical 

 investigations, which shall either confirm the observations of 

 Malpighi, Grew, Du Hamel, Mustel, and Hedwig, or prove 

 that plants have a special organisation of their own which is 

 more simple than that of animals, whether that organisation is 

 supposed to originate in simple peculiar fibres and threads 

 (Medicus) or with cellular and tubular tissue (tissu tubulaire 

 of Mirbel). Attention should also be given to the follow- 

 ing subordinate questions : i. How many kinds of vessels 

 may certainly be distinguished from the first period of their 

 development? The existence of certain forms having been 

 established ; 2. Are the twisted fibres which are called spiral 

 vessels (vasa spiralia) themselves hollow, and do they there- 

 fore form vessels, or do they serve by their convolutions for 

 the formation of closed cavities, and how? 3. Do fluids as 

 well as gases move in these cavities ? 4. Do the scalariform 

 ducts arise from adherence of the twisted threads (Sprengel), or 

 do the threads owe their origin to the ducts (Mirbel)? Do 

 alburnum and woody fibres originate in the scalariform ducts, 

 or in true vessels, or in tubular tissue ?' 



We see in this case as in many similar ones, that the subject 



