RAPIDITY OF CELL-PRODUCTION. 779 
the nucleus (jig. 1137, e, f, g) ; the daughter-stars of the dyaster 
thus produce a double basket appearance. The fibrils of these 
baskets next arrange themselves alter- 
nately, so that they seem to be trans- 
versely striated. A membrane next 
forms between the two divisions of 
the former nucleus (fig. 1137, h), i.e. 
between the two daughter-baskets 
whose fibrils now become convoluted, 
thus producing in the new nuclei an 
intranuclear network similar to that 
which existed in the mother-nucleus. 
These intracellular and intranu- 
clear networks, as well as the division 
of the nuclei, are well seen in rapidly 
forming cells, such as those in the 
growing points and ovules of plants. 
Rapidity of Cell-production.—By 
the ordinary method of cell-division, 
cells are in many instances produced we Ne we ee phase ot 
with almost inconceivable rapidity. ydeus (a) inthe embryo sac: 
Thus it has been stated that a fungus a, in Viola palustris; B, in 
of the Puff-ball genus has been known ey. Ci a oe 
to grow in a single night, in damp Be 
warm weather, from the size of a mere point to that of a 
large gourd; and it has been calculated, from the average 
size of its component cells, that such a plant must have con- 
tained at least forty-seven thousand million cells, so that they . 
must have been developed at the rate of nearly fowr thousand 
millions per hour, or more than sixty-six millions per minute. 
Another illustration of the rapid production of cells is afforded 
us in arctic and alpine regions, where it frequently happens that 
the snow over an extensive area is suddenly reddened by the Red 
Snow-plant (jig. 1). Again, it may readily be ascertained that, 
in a favourable growing season, many stems will increase three 
or four inches in length in twenty-four hours; thus the Agave 
americana or American Aloe, when flowering in our conserva- 
tories, has been known to develop its flower-stalk at the rate of 
at least a foot a day ; and in the warm climates where it is indi- 
genous, as in the Mauritius, it will grow at least two feet in the 
same period of time. Leaves also, in some cases, develop very 
rapidly ; thus, Mulder states that he has seen the leaf of Urama 
speciosa lengthen at the rate of from one and a half to three 
and a half lines per hour, and even as much as from four to 
five inches per day. In all these cases of rapid growth in size, 
it must be remembered, however, that the increase is due not 
only to the formation of new cells, but also to the expansion of 
those previously formed. 
In connexion with the rapidity of growth, it may be stated 
Fig. 1187. 
