Bryophytes are simple and truly land habiting plants present on moist shady places in tufts. They are small in size and range from few millimetres to few centimetres. Plant body is thalloid and leaf like. Plants are green in colour. Plants represent gametophytic generation which after fusion forms sporophyte which after reduction division form sporophyte which is called alternation of generation. Plants remain attached and absorption. Plants may be uni-cellular, multi-cellular and smooth walled or tuberculated. Internally the plant body does not show any vascular tissue like xylem or phloem. Gametophytic plant body reproduces both by vegetative and sexual means.
Sexual reproduction is of oogamous type and takes place by definite male Antheridium and female Archegonium reproductive organs. Antherozoids are motile biciliated structure produced in large numbers. Archegonium is a multi-cellular flask shaped organ having neck canal cells, neutral canal cells and an egg. Water medium is essential for fertilization. Fusion of antherozoids and eggs result in the formation of zygote or oospore which is diploid (sporophyte) in nature. Oospore develops into sporophyte which bears foot, seta and capsule. Spores are formed in capsule after reduction division. All spores are alike. Spores on germination give rise to gametophytic plant body usually through Protonema.
Inter relationship of Bryophytes with Algae: Botanists have given view that Bryophytes have evolved from Algae as under:
(1) Both Algae and Bryophytes have autotrophic mode of nutrition and green in colour.
(2) Cell wall is made up of cellulose.
(3) Presence of motile gametes (antherizoids ciliate).
(4) Necessity of Water at the time of fertilization.
(5) Poor development of vascular tissues.
(6) Heterotrichous habit and dichotomes branching.
(7) Reserve food material is starch.
According to Lignier in 1903 Algae gave rise to Prohepatics from which have arisen Bryophytes. Due to adaptation of land habit multi-cellular sex organs have become surrounded by a sterile jacket so as to protect them from the aerial conditions of drought. Bower thinks that the encircling of nucule on chara has also taken place for the same reason.
Inter relationship of Bryophytes with Pteridophytes:
Some botanists have given view that Bryophytes have originated from Pteridophytes as a result of reduction due to following reasons:
(1) Both groups have close similarity in the structure of sex organs i.e. antheridia and archegonia.
(2) There is distinct alternation of generation.
(3) The pigments, cell wall and reserved food material is chlorophyll, cellulose and starch in both fossil.
(4) The structure of sporangium of Anthoceros and fossil pteridophytes like sporogonites and Hornea is similar.
On the basis of these similarities above said botanists and Kashyap believe that Hepaticopasida (Bryophytes) have arisen from Pteridiophytes.
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