100 RJ, ANDERSON [AuGUST 
plant to consist of columns of dodecahedral cells, arranged so that 
the upper surface of one cell might coincide with the base of the one 
next above it. If the adjacent columns fit as nearly as possible into 
one another, that is to say, that the re-entrant angles of one column 
may correspond to the salient angles of the other, three dodecahedra 
will meet at each edge, but, since the angle of a dodecahedron is less 
than 120°, they will not fill the space, but will leave interstices, increas- 
ing In width from the centre of the mass towards its circumference. 
The “tubes ” will find room to grow in these interstices, and the growth 
will be effected by the addition of matter externally as in exogens. 
The increase is likely to be more considerable where the edges meet, 
that is, at the angles of the pentagon, than elsewhere. Certain quali- 
fications are, however, introduced. If the cells are icosahedral and 
arranged in the same manner, it is easy to see that, their angles being 
greater than 120°, the interstices would be formed internally, and that 
the growth of such a plant would proceed by the internal addition of 
matter as in so-called endogens. In this case, as in the exogens, the 
growth should take place along planes passing through the angular 
points. Hence the parts ought to be arranged in threes in the one 
ease and in fives in the first. The parts in the fructifying organs of 
certain fungi and mosses are in number powers of two, so, it is pointed 
out, that the cubical arrangement in acotyledons is rendered probable.’ 
This ingenious hypothesis (“ Une idée au moins piquante et ingénieuse,” 
says De Candolle) was propounded in the earlier years of the present 
century. The elements, although angular, unite to form tissues with 
round outlines. The form assumed is the result of various forces. 
Equally diffused pressure acting along the radu of a cylinder tends 
to maintain its form. A cone would have its shape best maintained 
by the diffusion of the pressure according to a certain law; but here 
again the internal activities, surface tension of cells, perhaps, and other 
agents, may materially modify the results. 
One cannot venture to compare the increase in size of a crystal to 
the deposit of a soluble salt from an evaporating solution, but rather 
to the growth of a battalion of soldiers by more men falling into rank 
all round at the word of command. Even in crystals many are the 
causes that affect the increase in size and form; temperature and 
impurities in the substance are two of the best known. The “ growth” 
here is, of course, influenced by the supply of material. Organic 
bodies, also, are influenced by many activities that start from without 
and reach into their substance. Their growth is true growth, but 
within considerable limits the physical demeanour of the organic may 
correspond to the inorganic. 
One might compare a slender shoot to a six-rayed ice crystal that 
is growing slowly by the addition of an upward stream of water. 
1 Abbreviated from Allman’s paper. The term ‘‘tubes” appears to have been used to 
indicate vessels and fibres of plants as distinguished from cells proper. 
