86 



LECTURE VI. 



appear to occur very commonly also elsewhere in the vegetable kingdom— the 

 number of the chlorophyll-granules increases somewhat proportionally to the increase 

 in surface of the growing cell-membrane. 



Jt may be reserved for other opportunities to treat of the properties of the 



chlorophyll colouring-matter, and of the grand 

 part which the chlorophyll-bodies play in the 

 vegetable kingdom as instruments of assimila- 

 tion ; and, finally, of the small starch-granules 

 commonly arising in them in consequence of 

 assimilation. Here it was only proposed to 

 state preliminarily the most necessary facts- 

 concerning the external appearance of the 

 chlorophyll-bodies. 



The cell-nucleus occurs, as already stated, 

 in the ordinary cells of the higher plants, 

 only singly in each cell as a rule. In very 

 long vesicular cells, and in the latex-tubes and 

 bast-cells, on the other hand, nuclei are present in larger numbers ; and in Algse and 

 Fungi it happens, when the cells are spacious or very long, that two, several, or 

 even hundreds and thousands of nuclei (which are then usually very small and 

 difficult to observe) exist in a celP. In accordance with its general behaviour, 

 the cell-nucleus may always be considered as a peculiarly individualised and sub- 

 stantially somewhat distinct part of the protoplasm, from which it is commonly 

 sharply separated in the form of a globular or ovoid mass, often lens-shaped 

 later, or rarely in the form of a more band-like or vermiform body. In older, still 

 living, vigorous cells, it commonly appears in the form of a vesicle; or a sphere 

 filled with granular substance, in which is almost always to be detected a so- 

 called nucleolus, or two, or even several. So far as the discussion (vigorously 



FIG. S3.— Embryos in the en^bryo sac of Altititn cepa 

 IJiey contain very large cell-iiuflei, each witll two nu. 

 cleoli. 



FIG. 84-— Cell-nuclei of Nothoscordon /rngrans (after Flemming). i. resting nucleus; 2. the nuclein 

 of the nucleus arranged in a filamentous coil-; 3. optical section of tha coil, where apparently only 

 granules are visible. 



revived of late) concerning the nature of the cell-nucleus allows the forming ot 

 an opinion, the nucleus consists ftf two kinds of substances: the main mass. 



■ More details concerning what has been stated in the text are found in my 'Text Book 

 of Botany.' With regard to what specially concerns the multi-nuclear cells, at that time (i.e. up 

 to 1874) still unknown, cf. Schmitz, Beobachtungen iiber die melkernigen Zellen der Siphonocladiaceen. 

 Festschrift der Naturforsch. Gesellsch., Halle, 1879. The same in Sitrungsber. der uiederrhein. 

 Gesellsch. fiir Natur- und Heilk., Bonn, 1880, June 7, and 1879, August 4. Treub, Sur les cellules 

 vigitales h. flusieurs noyaux, Archives neeilandaises t. xv. Johow, Untersuchungen iiber die 

 Zellkerne in den Secretbehdltern und Parenchymzellen der Monocotylen, Bonn, 1880. 



