90] CELL AND NUCLEAR DIVISION IN FULIGO VARIANS 245 
must also be borne in mind constantly that in such cleavage 
phenomena as these the cleavage planes are influenced in no 
way by the need of forming any specific tissue or plant form 
In the growing point of a metaphyte it may perhaps be difficult 
to decide whether the planes of division are determined by the 
cells themselves in accordance with internal conditions, or whether, 
as Sachs claims, it is the shape and differentiation of the shoot 
taken as a whole which determines the planes of division. In the 
division of these spore-forming masses no such question can arise, 
since no differentiated tissue is to be formed. The problem is 
simply to divide the large mass into smaller masses more con- 
venient for distribution. In doing this, as I have shown, entire 
megularity prevails as to the orientation of the cleavage planes 
with reference to each other, and with reference to the axes of 
the mass to be divided. It may be concluded that the proto- 
Plasm is per se perfectly isotropic so far as cleavage is concerned, 
and that it is a matter of indifference whether the cleavage 
planes intersect at right angles. If rectangular intersection is 
the rule in the higher plants, it might well be argued that this is 
*Sccondarily acquired condition, assuming with Pfeffer that 
these multinucleated structures are single cells. 
‘ _ can hardly be raised in this connection whether 
iiss: m : the cell forms the new cells or spores. Still it is. 
ik § and significant to note, as I have pointed out already / 
similar 1 toa of cleavage in these sporanges is essentially 
a. the typical cell division by constriction, 
eR mperibed as producing the one-nucleated cons at 
found i, Sa pee in the mildews, and which is also 
Muu CC t0Rtessive cleavage by suriace TES 
thon, ae modification of cell division by constric- 
Foheites eae is simply cell division, though not by 
in the es : ions of the mother cell, as it commonly occurs 
ret eit idea of the higher plants. ‘ 
a illustratin 88 the Multinucleatae cannot then be regarde 
logically Ais € growth of an organism comparable morpho- 
a metaphyte but without cell formation. The 
