APPENDIX. BOOK I. 
the chromatin fibrillse takes place, but he considers that two groups of fibriilse are formed 
which travel to the poles of the spindle; (3) he is of opinion that the equatorial plate 
consists of chromatin and the rest of the spindle of achromatin, whereas Strasburger 
states that the equatorial plate consists of the whole of the nuclear substance (both 
chromatin and achromatin) and that the spindle consists of cell-protoplasm ; (4) Flem- 
ming does not admit that the fibriilse, derived from the equatorial plate, which travel to 
each pole, undergo fusion to form a new nucleus, (See Quart. Journ. Micros. Sei. 1882.) 
The illustrative cases of cell-division which have been given in the text refer only to 
cells which contain a single nucleus. In cells which are or are about to become multi- 
nuclear, — in cases, that is, in which nuclear division is not followed by cell division,— 
the process of nuclear division is usually simpler. In the older internodal cells of the 
Characeae, in older parenchymatous cells of Lycopodium and of some Phanerogams 
{Taraxacum, Glyceria, Sempervi'vum, Cereus, Solanum, etc.), and occasionally in Falonia (in 
all of which cases the cells become multinuclear), the nucleus simply divides by con- 
striction, the chromatin granules being shared equally between the two new nuclei 
without any indications of karyokinesis. Division may begin again in the two new 
nuclei even before they are separated from each other. This process of nuclear division 
has been termed fragmentation. In Valon'ta and in Codlum a rudimentary form of karyo- 
kinesis has been observed by Schmitz and by Berthold (Mittheil, der zool. Stat, zu 
Neapel, II, 1880), which appears to occur commonly among Thallophytes. In such a case 
the nucleus becomes elongated ; its ends enlarge, whereas the middle part remains narrow ; 
the ground-substance of the nucleus now presents a faint longitudinal striation, and the 
chromatin-granules either simply travel to the two ends of the nucleus, or become rod- 
shaped and aggregate in the equatorial plane to form a rudimentary nuclear disc, which 
splits in the ordinary way, each half travelling to one end of the nucleus. The narrow 
middle portion now undergoes absorption, and the two ends round themselves off to con- 
stitute two new nuclei. Treub (Sur des cellules vegltales ä plusieurs noyaux, Arch. 
N6erland., XV, 1880) has observed the division of the nucleus in the multinuclear bast- 
fibres and laticiferous cells of various Phanerogams, and finds that it takes place in the 
manner described in the text for uninuclear cells, except that no cell-plate is formed. 
See also Johow, Die Zellkerne von Char a, Bot. Zeitg. 1881. 
An illustration of the independence of cell-division with regard to nuclear division 
is aß'orded by Cladophora. The cells of this plant are multinuclear, and Strasburger has 
found that the division of the nuclei takes place in the manner observed by Treub in 
bast-fibres and laticiferous cells : the division of the cells bears no relation, either in 
time or space, to that of the nuclei ; the new cell-wall is formed in much the same 
manner as in Spirogyra. 
Page 19. Schmitz has come to the conclusion {loc, cit. 1880) that the cell-wall is 
formed by the actual conversion of a peripheral layer of the protoplasm into cellulose. 
He is also of opinion that stratified cell-walls are formed by the deposition, one within 
the other, of successive layers, and not by intussusceptive growth with subsequent difi'er- 
entiation. These views are also held by Strasburger ; Bau und Wachsthum der Zell- 
häute, 1882 (see p. 960). 
Both Schmitz and Strasburger hold that the surface-growth of cell-walls is not due 
to the intercalation of new solid particles (intussusception), but is simply the expression 
of the stretching of the cell-wall by the cell-contents. 
Frommann (Protoplasma, 1880) believes that he has been able to trace a connexion 
of the protoplasm through the walls of adjacent cells. That protoplasm can pass through 
closed cell-walls is beyond doubt. See Strasburger, loc. cit. p. 247. 
Page 23. The formation of bordered pits. A very different account from that in 
the text is given by Mikosch (Unters, üb. Entstehung und Bau der Hoftüpfel, Sitzber. d. 
k. k. Akad. in Wien, LXXXIV, 1881). Sachs has found (Ueb. die Porosität des Holzes, 
Arb. d. bot. Inst, in Würzburg, II, 1879) that in the spring-wood at least the bordered pits 
are closed by a membrane. See also Strasburger, Bau und Wachsth. d. Zellhäute, 1882. 
