Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
262
Pontederiaceae.
Because of the suggested close relationship of this family with
‘the order of Helobiales it is of interest to note that at least one
representative of Pontederiaceae,
Heteranthera reniformis
displays a striking resemblance in the general features of pollen
formation with the members of the order mentioned. Not only is
the successive bipartition the rule, as far as I have seen, without
exception, but also a tapetum is formed out of the peripheral parts
of the sporogenous tissue.
Stemonaceae.
In this family I have been able to record the pollen development
for the two species
Siemona moluccana Engl. and S. javanica Engl. Both species show
successiv bipartition. The spore mother cells are remarkably small,
augmenting but little in size during the divisions, and their walls
remain very thin. The general appearance of microsporogenesis here
agrees closely with e. g. Flagellaria.
Liliaceae.
The mode of pollen formation is now known for a comparatively
great number of species belonging to this family, and it has been
ascertained that both bipartion and quadripartition occur in mem-
bers systematically quite nearly related. In this connection it is
perhaps worth mentioning that an analogue variation in the deve-
lopment of the female gamophyte has been found.
I have observed the successive bipartion in
Sanseviera macrophylla Wallr. and
Eustrephus latifolius R. Br.
A very illustrative exemple of quadripartition is
Dianella spec.
Here a complete series of stages made it possible to make a
detailed account of the formation of the partition walls in the
spindles after the second division of the mother cell. No traces of
a cell plate could be seen during the heterotypic division.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
