66
H. W A M S AND P. KALLIO
the length of the (biradiate) diploid to the length of the haploid is 1 : 24
in M. thomasiana var. notata, 1 : 20 in M. torreyi, 1 : 25 in M. fimbriata
and 1 : 15 in M. angulosa (Kallio, 1957). The ratios of the widths of
the haploid and diploid cells differ from these values, the diploids
being always relatively wider than the haploids, and hence the shapes
of the two cell types differ. The ratios of width to length in the haploid
and diploid cells are 0 : 92 and 0 : 96 in M. thomasiana, 0 : 88 and
0 : 95 in M. torreyi and 0 : 85 and 0 : 87 in M. fimbriata. The
volume of the diploid is about twice as large, but often more, as the
volume of the haploid; e.g. the ratio of the volumes in M. thomasiana
has been estimated at about 2 : 3 .
The lobes are relatively wider in diploids than in haploids. In the
haploid the angle between the longitudinal axis and the sinus edge is a
right angle, but in the diploid the angle is larger, in M. thomasiana often
about 110°. The widths of the different lobes do not change similarly
on ploidization, however. The lower side lobe usually reacts more
sensitively than the other lobes although there are differences in this
respect in different species. The morphological differentiation in the
subdivision of the lobes has proceeded further in the diploids. For
example, in the haploid M. thomasiana var. notata the side lobes are
divided into two secondary lobes and each of the latter into two tertiary
lobes and so on, until the fourth division has finally resulted in the outermost indentations. In the diploid the number of these divisions is one
greater, giving thirty-two teeth as compared with sixteen in eth haploid.
In optimal conditions the chloroplast mass as well as the number of
pyrenoids increases in the same ratio as the cell volume.
In all species studied the morphological variation of diploids is
greater than that of haploids, the diploids being more sensitive to
variations in environmental conditions than the haploids. One characteristic feature only rarely seen in haploid cells is common to all diploid
species : the side lobes have a tendency to undergo doubling. The lobes
are either totally or only partially double and the subunits are simpler
in form than the normal lobes. The different lobes show a varying
tendency to undergo this 'lobe doubling'. In M. thomasiana var, notata,
M. rotata, M. angulosa and M. torreyi, the upper side lobe is the most
sensitive, whereas in M. thomasiana type form and M. denticulata the
most sensitive is the lower side lobe. Sometimes bifurcation of the polar
lobe has been observed (Grönblad and Kallio, 1954).
The rate of cell division varies greatly with the environmental conditions, but when cultivated in the same culture vessels with the
haploids, the diploids always divide at a lower rate (cf. Kallio, 1951,
1961). The diploid form is more sensitive to adverse conditions; the
temperature maximum for clone growth is lower for diploids than for
H. W A M S AND P. KALLIO
the length of the (biradiate) diploid to the length of the haploid is 1 : 24
in M. thomasiana var. notata, 1 : 20 in M. torreyi, 1 : 25 in M. fimbriata
and 1 : 15 in M. angulosa (Kallio, 1957). The ratios of the widths of
the haploid and diploid cells differ from these values, the diploids
being always relatively wider than the haploids, and hence the shapes
of the two cell types differ. The ratios of width to length in the haploid
and diploid cells are 0 : 92 and 0 : 96 in M. thomasiana, 0 : 88 and
0 : 95 in M. torreyi and 0 : 85 and 0 : 87 in M. fimbriata. The
volume of the diploid is about twice as large, but often more, as the
volume of the haploid; e.g. the ratio of the volumes in M. thomasiana
has been estimated at about 2 : 3 .
The lobes are relatively wider in diploids than in haploids. In the
haploid the angle between the longitudinal axis and the sinus edge is a
right angle, but in the diploid the angle is larger, in M. thomasiana often
about 110°. The widths of the different lobes do not change similarly
on ploidization, however. The lower side lobe usually reacts more
sensitively than the other lobes although there are differences in this
respect in different species. The morphological differentiation in the
subdivision of the lobes has proceeded further in the diploids. For
example, in the haploid M. thomasiana var. notata the side lobes are
divided into two secondary lobes and each of the latter into two tertiary
lobes and so on, until the fourth division has finally resulted in the outermost indentations. In the diploid the number of these divisions is one
greater, giving thirty-two teeth as compared with sixteen in eth haploid.
In optimal conditions the chloroplast mass as well as the number of
pyrenoids increases in the same ratio as the cell volume.
In all species studied the morphological variation of diploids is
greater than that of haploids, the diploids being more sensitive to
variations in environmental conditions than the haploids. One characteristic feature only rarely seen in haploid cells is common to all diploid
species : the side lobes have a tendency to undergo doubling. The lobes
are either totally or only partially double and the subunits are simpler
in form than the normal lobes. The different lobes show a varying
tendency to undergo this 'lobe doubling'. In M. thomasiana var, notata,
M. rotata, M. angulosa and M. torreyi, the upper side lobe is the most
sensitive, whereas in M. thomasiana type form and M. denticulata the
most sensitive is the lower side lobe. Sometimes bifurcation of the polar
lobe has been observed (Grönblad and Kallio, 1954).
The rate of cell division varies greatly with the environmental conditions, but when cultivated in the same culture vessels with the
haploids, the diploids always divide at a lower rate (cf. Kallio, 1951,
1961). The diploid form is more sensitive to adverse conditions; the
temperature maximum for clone growth is lower for diploids than for