Datos para la flora algológica de nuestras aguas dulces - Jolube ...

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120
/llstilulo Botánico de Baree/olla
but they have not been denominated, be'eause it \Vas UIleertain
whether they might have been already deseribed.
Firstly, some general biocenologieal questions are' treated
and diseussed in the seeond part of the memoir, so that
they may serve as an introduetion to the subsequent pages
(Chapters 1-2). :By eomparing the eomposition of the diHerent
samples, the existeneo of a determinate number of
associations may be tixed, (Ohapt. 3-4). The tables inserted
in the Spanish text show clearly the eharaeteristies and
principal eomponents of these diHerent eommunities. They
aequire a real eonsisteney when ordered and grouped by
their eeologieal and sueee'ssional features in' multiple series
(see pieture B).
Comparison of the material available from the enviro)l­
.ments of Barcelona to that of the mountainous eountry of
the Montseny, lead us to the essenee of the regional diversitieation
of limnologieal vegetation, notwithstanrling that
both distriets are separated by only 55 kilometers (Chapt. 5).
The last ehapter (6) dwells on the inf1nenee that ambient
eonditions have upen the algae, speeially upon the heleoplanktonie
ones. For laek of the proper means of measuring
the medium faCtors, due to the author's limited resourees,
lhe value of these observations is somewhat diminished.
An inerease oI the temperature, of. the dissolved salts
and of the pH (that is, in synthesis, an inerease of the eutrophy
of the water), determines, generally, a diminution in
size of the organisms amI strengthens the eharaeteristies
eonsidered to be adaptations to a f10ating existenee. This
intraspeeitie and experimental variation may be eompared
and related to the eeologieal -perhaps phY'logenetie to- series
of very affined speeies, sueh as are observed in many genera
(GompllOspllaeria, Scenedesl1"'s, Synedra, tables 20-211).
Along these hypothetical lines of evolution and going through
their growing eutrophilia, may be observed an augmentation
of the eharaeleristies of adaptation to planktonieal !ife.
This harmonizes perfeetly, taking into aeeount the' faet that
luxuriant swimming vegetation developes only in very nutritious
waters, and ·that in a warm ambient, rieh in salts,
the apparition and seleelion of proper mutants is easier.
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