12 
ORGANOGRAPHY. 
BOOK I. 
Mohl, whose researches show that this mode of generating 
cellular tissue is far from universal, as might indeed have 
already been suspected from what is known of the formation 
of pollen grains. It appears that in Confervae the increase in 
number of the cells takes place by the internal division of the 
parent cells. In Conferva glomerata the last joint is always 
as long as those below it, only rather more slender. The 
branches grow at the upper lateral extremity of a joint or 
cell ; each at first is a small protuberance, which is trans- 
formed into a lateral cylindrical excrescence containing chlo- 
rophyll (green colouring matter), and having its cavity in 
communication with that of the joint which bears it; as the 
branch lengthens, a contraction is observable at the line of 
insertion, which contraction is directed towards the interior 
of the cell, and chokes up the green matter, forming a sort of 
partition, pierced in the middle like a ring. This partition 
grows with the growth of the branch, and at last completely 
cuts off all communication between the first cell and its 
branch. Thus cut off, the latter lengthens by degrees, till 
it forms a very long cylindrical cell, which divides in just the 
same manner into two other cells, the terminal of which alone 
lengthens, to be again bisected in its turn. 
Schleiden’s ideas as to the origin of cells are still different 
from all these : see page 20. 
The bladders develope, in some cases, with great rapidity. 
I have seen Lupinus polyphyllus grow in length at the rate 
of an inch and a half a day. The leaf of Urania speciosa has 
been found by Mulder to 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. But the most remarkable 
instances of this sort are to be found in the mushroom tribe, 
which in all cases develope with surprising rapidity. It is 
stated by Junghuns, that he has known the Bovista gigan- 
teum, in damp warm weather, grow in a single night from 
the size of a mere point to that of a huge gourd. We are 
not further informed of the dimensions of this specimen ; but 
supposing its cellules to be not less than the 
in diameter, and it is probable they are nearer the it 
may be estimated to have consisted, when full grown, of about 
