NOTES 705 



would therefore prefer to term the subject-matter of Vochting's work " ontogenetico- 

 physiological " (entwickelungsmechanische or t ntwich lungsphysiologischt ) anatomj . 

 This last- mentioned aspect of anatomy naturally cannot claim to be the only experi- 

 mental branch of the science ; in the same way the " phylogenetic anatomy " of 

 Strasburger and his pupils cannot be regarded as the only legitimate " comparative 

 anatomy." On the contrary, every anatomical investigation must follow comparative 

 lines, if it is to lead to results of scientific value (cf. second [German] edition, p. 2). 



2. The functional units are not always exactly identical with the formal units or 

 cells. Thus, in the case of palisade-tissue, the functional unit (palisade-unit) may, 

 and usually does, consist of a single cell ; it may, on the other hand, represent a 

 branch of a cell, every cell being made up of 2 to 4 palisade-shaped branches or "arms." 

 The functional units of mechanical strands are the individual mechanical fibres. 

 As a rule every fibre consists of a single morphological unit or cell. A septate bast- 

 fibre, however, comprises more than one cell, while every eollenchyma "fibre" 

 is made up of the thickened edges of the walls of several adjacent cells. The functional 

 units of the conducting system are the individual water-conducting tubes, but any 

 given tube may consist of a single cell (tracheid) or of a row of fused cells (wood- 

 vessel). These facts show that plants do not always maintain the individuality of 

 the cell in constructing their functional units ; in other words, the limits of functional 

 unit are not always marked by cell-walls. Such exceptional cases do not, however, 

 necessitate any departure from the long-established and, on the whole, fully justified 

 view which regards the cell as the general functional unit of the plant-body. 



3. G. Haberlandt : Sitzb. Wien, 111 (1902) [experiments with isolated cells]. 



4. The fact that, at the present time, the scientific conception of the structural 

 units does not coincide with the traditional notion of the cell, occasionally causes 

 some inconvenience, especially from a didactic point of view. Strictly speaking, 

 for example, it is a contradiction in terms to call a naked swarm-spore a " cell." 

 Sachs accordingly proposed (Flora, 1892) to restrict the term cell, so far as Botany 

 is concerned, either to the cell-wall alone or to the cell-wall plus the cell-contents. 

 The " morphological and physiological organic unit," consisting of a nucleus and the 

 area of protoplasm controlled thereby, Sachs proposes to call an energid. So far as 

 ordinary uninucleate cells are concerned, " energid " corresponds exactly to Hanstein's 

 " protoplast " or Briicke's " cell- body " (Zellenleib). In the case of multinucleate 

 cells and syncytes, on the other hand (latex-tubes and many bast-fibres), and among 

 the non-cellular Siphoneae and Phycomycetes, Sachs regards each protoplast as made 

 up of as many energids as there are nuclei. In such cases it is impossible to make out 

 the hypothetical limits of the individual energids ; hence the latter cannot be 

 regarded as morphological units. It is also quite uncertain whether each nucleus, 

 in a multinucleate protoplast, permanently exercises entire control over a definite 

 tract of protoplasm (as Zimmermann has remarked, it is impossible to conceive of 

 any such permanent relation in the case of a multinucleate cell which exhibits active 

 protoplasmic circulation) ; the energid therefore appears an unsatisfactory unit 

 from the physiological, as well as from the morphological, point of new. The diffi- 

 culty is not restricted to the case of multinucleate cells ; for, in most living tissues, 

 the protoplasts of adjoining uninucleate elements are connected by means of proto- 

 plasmic filaments, and it cannot be assumed that the influence of the nuclei is never 

 transmitted along these protoplasmic connections from one cell to another. Evi- 

 dently, in defining the " organic unit " of the plant- or animal-body, it will not do 

 to lay stress upon the still largely mysterious interrelations between any one consti- 

 tuent part of that unit and the remaining components, far less to make these inter- 

 relations the basis of our definition. 



2 y 



