Iyengar, M. O. P.

English

Publications of the IAS Fellows

[329]
FRITSCHIELLA, A NEW TERRESTRIAL
MEMBER OF THE CHAETOPHORACEAE
BY M . O. P . I Y E N G A R
Department of Botany, East London College,
University of London
(With Plate XIII and 2 figures in the text)
THIS alga was growing more or less gregariously, together withProtosiphon botryoides or Botrydium tuberoswn, on the moist silt
of drying rain-water pools at Madras and occurred in a similar
situation, together with Botrydium tttberosmn, at Talguppa in the
Mysore Province. The alga has been repeatedly observed in Madras in
different years, when the pools were drying up after the north-east
monsoon.
At first sight the alga recalls a dense growth of Siigeoclonium, but
careful examination shows that it possesses a complicated structure
which is much more specialised than that of the latter genus. The
mature plant consists of (i) a rhizoidal system, penetrating the sub-
stratum and comprising one or more downwardly directed rhizoid-
like filaments made up of much elongated eolourless cells with very
scanty contents and sometimes with a few branches (Text-fig. 2, A,
Text-fig. I, F); (2) a prostrate system composed of a number of
rounded or irregular swollen clusters of cells with dense contents and
thin walls, the whole forming an irregular system with short congested
branches (Text-fig. 2, A, C, H, cl); (3) a primary projecting system,
arising from the prostrate system and consisting of a number of
upright short-celled branched threads (Text-fig. 2, A, H, pr); and
(4) a secondary projecting system composed of somewhat elongate
branches having longer cells with bright green contents (Text-fig.
2, A, H, sec). In the natural habitat only the secondary projecting
system arises as a tuft above the surface of the substratum, the
remaining portions of the alga being situated on a level with or
slightly beneath the surface of the soil.
The development ofthe mature structure. As far as can be made out
from preserved material, the alga seems to develop in the following
manner. In the youngest stage it appears as an unbranched erect
330 M. O. P. IYENGAR
Te.\t-fig. I. Fritschiella iuberosa sp.n. A-F, various stages of growth of the
young plants. G-I, plants with only the rhizoidal and prostrate systems of
clustered cells developed; in G a side branch is forming a second rhizoid.
cl, clusters of cells belonging to the prostrate system; r, rhizuid. E •. 600;
/ ,-, Soo; the rest ^400.
Fritschiella, a new member of Chaetophoraceae 331
-c/
Text-fig. 2. Fritscliiella tithcrosa sp.n. A, a small mature plant with a single
rliizoid. C, portion of a mature plant. B. D, G, parts of branches belonging
to the secondary projecting system. E, F. portions of the primary pro-
jecting system. H, part of a plant showing all the various systems. / , a
portion of a prostrate sj'stcm with a branch of the primary projecting
system, cl, cluster of cells of the prostrate system; r, rhizoid; pr, primary
projecting branches; sec, secondary projecting branches. D .-,500; the
rest ,•: 350.
332 M. O. P. IYENGAR
filament composed of a few cells and probably largely buried in the
substratum. The uppermost cells are somewhat wider with richer
contents and form a linear row of four cells (Text-fig, i. A, B). The
lower cells are elongate and form a rhizoid which, as mentioned above,
may branch once or twice or remain unbranched. Earlier stages than
this were not observed.
Each of the four cells terminating this primary filament enlarges
and divides into four; the division of the lower cells is generally
transverse, while in the upper ones transverse, longitudinal and
diagonal divisions are seen (Text-fig, i, C-E). The resulting cells
continue to divide in all directions, though mainly along planes at
right angles to one another, so that ultimately an irregular group of
rounded cell clusters is formed, each cluster being the result of the
continuous division of one of the four original cells or of one of their
products (Text-fig, i, D-F). In many of these clusters localised
growth occurs, so that new clusters are budded out laterally or the
whole grows out to one side, usually in a slightly downward direction
(Text-fig. I. G~I, Text-fig. 2,C, I: PI. XIII, i, 3, 5-9). In the latter
case the end cell growsout into a long rhizoid (Text-fig, i, G; PI. XIII,
I, 5). Sometimes a number of rhizoids are formed in this way. In
many cases, however, downward growth of the clusters does not
occur and then the entire plant has only the single original rhizoid
(Text-fig. 2, .1, C, H; PI. XIII, 3, 6, 9).
Erom some of these rounded clusters of cells, representing the
prostrate system of the alga, but usually from the uppermost ones, a
number of filaments grow upwards. These, forming the primary
projecting system, are composed of short cells whose length and
breadth are very nearly equal (Text-fig. 2,A,H,I\pr,E, F; PI. XIII,
1-7), and which have fairly dense contents. Division in these threads
mostly takes place transversely, though occasional longitudinal,
cross-wise, or diagonal division may occur (Text-fig. 2, E, F).
Rounded clusters, like those seen in the prostrate system, are,
however, never formed. The primary branches show considerable
ramification, all the threads growing upwards.
Erom the upper ends of these primary branches then arise a
number of secondary branches {secondarv projecting system), com-
posed below of much elongated cells with scanty contents and above
of comparatively shorter cells with dense bright green contents. The
latter, with the exception of the terminal cell, generally grow out
laterally into a short branch usually not separated by a septum from
the parent cell, though occasionally a septum may be formed
Fritschiellaj a new member of Chaetophoraceae 333
(Text-fig. 2,A,H [sec], B,D,G; PI. XIII, 2); these branches have a
broad conical apex. No hairs of any kind are formed on any of the
branches.
In the cells of the secondarj^ projecting sj'stem a curved plate-
shaped chloroplast with 2-8 pyrenoids is well seen (Text-fig. 2,
B, D, G). But in those of the primary projecting and the prostrate
systems the contents are very dense and the chloroplast is not clearly
recognisable. The pyrenoids in these latter cells are smaller and fewer
in number (usually 2-4) than in those of the secondary' projecting
system. All the cells have a single nucleus. The walls are in no way
thickened.
In the material it was not unusual to find plants lacking the
secondary system, or possessing only the prostrate and rhizoidal
systems (PL XIII, 5); such plants represent immature stages which
have yet to complete their full growth. Very often one or other of the
four systems is especially prominently differentiated. The prostrate
system varies very much in the extent of its development. In young
plants it is generally small, but it gradually increases in size as the
plant grows older, well-grown specimens invariably showing a very
well-developed prostrate system.
The rounded clusters of cells constituting the prostrate system
and composed of small cells with thin walls and dense contents are
very peculiar and hitherto quite unknown among Chaetophoraceae.
Their exact function is not clearly established. They remind one to
some extent of the swollen upper portions of a Schizomeris filament
before the walls break down and the contents escape as zoospores.
It is probable that they serve for the perennation of the alga during
the long dry season.
Algae like Botrydiuni, Protosiphon and FritscliicUa growing on the
moist earth of drj-ing pools are always in danger of rapid desiccation,
and must be able to meet this contingency in some fashion. As long
as the soil is moist they grow and increase in size. When conditions of
desiccation set in, the contents of Botryduim and Protosiphon recede
into the underground portions of these plants and form cj'sts which
rest unharmed until the next rainy season. The new plants arise
from the contents of the cysts either directly or indirectly by the
formation of motile spores. In the case of Botrydiiim and Protosiphon
the protoplasmic contents can readily migrate into the underground
portions as a result of the coenocytic structure. But in the case of
Fritschidla the septate structure of the alga renders such a migration
impossible. It is probable that the cell clusters of the prostrate
334 M- O. P. IYENGAR
system serve as a means of perennation which is prepared long be/ore
it becomes acliiaUv iwccssarv to meet tlie danger of sudden desiccation.
In fact, as already mentioned above, the alga continues to form these
perennating clusters of cells from the very beginning of its life, so
that they may be available for an emergency at any stage of its
existence. The cells themselves with their dense contents and scanty
vacuoles appear well fitted for a resting period without further
preparation. No special thickening of the walls has been observed,
though the outer wall of each cluster was decidedly thicker than the
walls between adjacent cells of the cluster. The thin walls of the
individual cells of each cluster will facilitate the escape of motile
spores, if such, as seems probable, should be formed in these cells
when the rainy season commences.
The clusters of cells show a certain remote resemblance to the
appearance obtained during the early staf;es of palmella formation
in certain species of Stigcoclo)!!in)i. But in a terrestrial alga like
F I'll sell iclln the growth of cells, isolated during palmella formation, will
lead to a dense growth of new plants at one place. The rather uni-
formly distributed, though gregarious, growth of the alga on the bed
of the pool and the absence of any dense clusters suggest zoospore
formation rather than development from a palmella stage.
Numerous plants were carefully examined for empty cells from
which motile spores could have escaped, but no such cells were found
either in the prostrate or in the projecting systems. It can hardly be
doubted that when the soil dries up the projecting sj'stem perishes,
so that this system is probably purely assimilatory in function,
affording an interesting instance of division of labour among the
Chaetophoraceae.
In the absence of knowledge of the motile stages of the alga, it is
not easy to decide its systematic position. The general appearance of
the uppermost branches (secondary projecting system) and of their
cells and to some extent also that of the primary projecting system
much resemble Stigeoelonium. In the possession of rhizoid-like
filaments and the terrestrial habit there is similarity to Iwanoffia
Pascher^ {Stigeoeloniuiii terrestre Iwanoff). It differs markedly from
Iwanoffia, Stigeoeloniiim and all the other members of the Chaeto-
phoraceae in its special hal)it, in the formation of a prostrate system
composed of clusters of cells that probably pcrennate and in the high
specialisation of its thallus into rhizoidal, prostrate, primary and
secondary projecting systems. The alga may therefore' be regarded as
1 A. Paschcr, Bibl. Bol. 67, 63. 1907.
THE NEW PHYTOLOGIST VOL. XXXI, PLATE XIII
IYENGAR—FRITSCHIELLA
Fritschiella, a new member of Chaetophoraceae 335
the type of a new genus of Chaetophoraceae alhed to Iwanoffia and
Stigeoclonium which I shall call:
FritsckieUa gen.nov.
Thallus terrestrial, branched above and attached to the soil by
means of colourless septate rhizoids, with a number of irregularly
rounded clusters of small cells with dense contents and thin walls
forming a crowded prostrate system probably serving for purposes of
perennation, and a projecting system composed of a lower portion
consisting of very short cells and an upper portion consisting of
elongate cells, bearing some branches; setae absent; zoospores and
gametes not observed.
Fritschiella tuberosa sp.n. (Text-figs, i & 2; PI. XIII).
Characters same as for the genus; cells of the upper branches
6-iO/x broad and 3-8 times as long as broad, those of the lower
branches 7-11/^ broad and 5-iOfi long; perennating clusters of the
prostrate system about 18-40/x in diameter; rhizoidal filaments
4-8/x broad; plants without the rhizoids about 250-600/x high.
Habitat. On moist silt on the bed of drying rain-water pools at
Madras, and Talguppa in Mysore Province, India.
In conclusion the writer wishes to express his indebtedness to
Prof. F. E. Fritsch, F.R.S. for his guidance and help in preparing this
paper.
EXPLANATION OF PLATE XIII
Fritschiella tuberosa sp.n.
I, 3, 4, 6, plants showing habit: 2, primary and secondan^ projecting
systems; 5, young plant with'only prostrate and rhizoidal systems developed,
with a branch of the primary projecting s}fstem beginning to form; 7, 8, a
portion of 4 enlarged; 9, a portion of 6 enlarged, d and d, prostrate system;
pr, primary projecting system; sec, secondary projecting system; r, rhizoid.
7, 9 xabout 200; 8 xabout 350; the rest xabout 100.



Fritschiella, a new terrestrial member of the chaetophoraceae

Indian Academy of Sciences

http://repository.ias.ac.in/28108/1/28108.pdf

Fritschiella, a new terrestrial member of the chaetophoraceae

Abstract

Similar works

Full text

Available Versions

Publications of the IAS Fellows

Indian Academy of Sciences