1.7 Disaccate Forms
15
The former was erected to accommodate disaccate forms possessing a trilete
proximal mark, and the latter for disaccate forms not possessing one; or possessing
a monolete proximal mark. It appears that Leschik (1965, p. 54) interpreted the
proximal scar as a germinal aperture. This phenomenon is not known among today’s
saccate pollen grains which are known to germinate distally. Ancient saccate pollen
grains had similar ways of germinating as seen from the studies of cappula which
is always a thinner area in the exine, and is also observed in the present study in
disaccate pollen.
Again, as in the case of the monosaccate forms, dividing the disaccates on the
basis of the characteristics of the tetrad mark would lead to splitting of genera among
different supra-generic groups and leading to the formation of artificial species. A
fact clearly demonstrated from the studies of the pollen of Ulmania frumentaria is
described and illustrated by Potonie and Schweitzer (1960). The variations in the
tetrad mark in U. frumentaria are obvious, passing from monolete to dilete or trilete
and from a clearly outlined scar to a vaguely visible one. The same has been observed
in the present study of Potoniesporites which ranges from monolete to dilete, trilete
or inaperturate.
Bharadwaj (1958) erected a new series; SULCATI for sulcate disaccate forms.
Series sulcati could be used to accommodate such forms as Falcisporites Klaus,
pollen grains of Caytonanthus, which according to Harris (1951) possess “a groove
or a slit on the distal face”. Series sulcati is not used in the present study simply
because only one pollen grain suggesting a sulcate disaccate pollen morphology has
been observed in the present samples. It is also noteworthy that no such structure has
been found in saccate pollen grains of living plants.
1.8 Striatiti
The proximally taeniate saccate pollen forms are described in the present study
under the group STRIATITI (Pant 1955) which is raised here from infra-turma to
sub-turma to accommodate all saccate pollen possessing a taeniate cappa regardless
of the orientation of taeniae, whether transverse or vertical, and regardless of the
character of the sacci, whether disaccate, monosaccate, lobed or rudimentary sacci.
The infra-turmae STRIASACCITI and DISTRIASACCITI, proposed by Bharadwaj
(1962) for monosaccate forms possessing taeniae on one face of the corpus and on the
two faces of the corpus, respectively, are not used in the present study. Monosaccate
taeniate forms could possibly be monstrosities of disaccate striatiti, as noted by Hart
(1965). The monosaccate or lobed taeniate forms are accommodated here under subturma STRIATITI. The striatiti have no equivalent in presently living pollen; they
represent an extinct group. Striate pollen has been isolated from sporangia attached
to Glossopteris wood. These studies have therefore clearly demonstrated them to be
the pollen of the Glossopteris. Moreover, the same studies (Lindstrom et al. 1997)
found extreme variations among several thousand pollen grains released from one
sporangium; from trisaccate to bisaccate, monosaccate or lacking in sacci entirely.
15
The former was erected to accommodate disaccate forms possessing a trilete
proximal mark, and the latter for disaccate forms not possessing one; or possessing
a monolete proximal mark. It appears that Leschik (1965, p. 54) interpreted the
proximal scar as a germinal aperture. This phenomenon is not known among today’s
saccate pollen grains which are known to germinate distally. Ancient saccate pollen
grains had similar ways of germinating as seen from the studies of cappula which
is always a thinner area in the exine, and is also observed in the present study in
disaccate pollen.
Again, as in the case of the monosaccate forms, dividing the disaccates on the
basis of the characteristics of the tetrad mark would lead to splitting of genera among
different supra-generic groups and leading to the formation of artificial species. A
fact clearly demonstrated from the studies of the pollen of Ulmania frumentaria is
described and illustrated by Potonie and Schweitzer (1960). The variations in the
tetrad mark in U. frumentaria are obvious, passing from monolete to dilete or trilete
and from a clearly outlined scar to a vaguely visible one. The same has been observed
in the present study of Potoniesporites which ranges from monolete to dilete, trilete
or inaperturate.
Bharadwaj (1958) erected a new series; SULCATI for sulcate disaccate forms.
Series sulcati could be used to accommodate such forms as Falcisporites Klaus,
pollen grains of Caytonanthus, which according to Harris (1951) possess “a groove
or a slit on the distal face”. Series sulcati is not used in the present study simply
because only one pollen grain suggesting a sulcate disaccate pollen morphology has
been observed in the present samples. It is also noteworthy that no such structure has
been found in saccate pollen grains of living plants.
1.8 Striatiti
The proximally taeniate saccate pollen forms are described in the present study
under the group STRIATITI (Pant 1955) which is raised here from infra-turma to
sub-turma to accommodate all saccate pollen possessing a taeniate cappa regardless
of the orientation of taeniae, whether transverse or vertical, and regardless of the
character of the sacci, whether disaccate, monosaccate, lobed or rudimentary sacci.
The infra-turmae STRIASACCITI and DISTRIASACCITI, proposed by Bharadwaj
(1962) for monosaccate forms possessing taeniae on one face of the corpus and on the
two faces of the corpus, respectively, are not used in the present study. Monosaccate
taeniate forms could possibly be monstrosities of disaccate striatiti, as noted by Hart
(1965). The monosaccate or lobed taeniate forms are accommodated here under subturma STRIATITI. The striatiti have no equivalent in presently living pollen; they
represent an extinct group. Striate pollen has been isolated from sporangia attached
to Glossopteris wood. These studies have therefore clearly demonstrated them to be
the pollen of the Glossopteris. Moreover, the same studies (Lindstrom et al. 1997)
found extreme variations among several thousand pollen grains released from one
sporangium; from trisaccate to bisaccate, monosaccate or lacking in sacci entirely.