Beginner’sCorner Beginner’s corner
found in the axil of a modified leaf (bract). The archegonium is flask-shaped with a long neck and Capsule Liverwort swollen base which contains an egg cell. Between species, the appearance of the individual sexual Seta organs does not differ much.
Leafy liverworts reproductive structures – Perianth When fertile, most British leafy liverworts develop a perianth, a tube-like structure formed by the fusion of a few leaves that surrounds and protects Female (perichaetial) demystifying the jargon the developing capsule. Perianths are typically bract longer-lived and more distinctive than the capsules themselves, which may take up to a year to develop. Size, shape and other characters vary between nderstanding the terms used to In this edition of Beginner’s Corner Sharon species and can be important diagnostic features. For example, the characteristic ‘star-like’ perianths describe liverwort structures and Pilkington turns her attention to the Leafy shoot knowing what they look like and of the Lejeuneaceae are produced by folds in the where to find them is fundamental confusing and difficult subject of liverwort perianth. to identification. Many bryological reproductive structures that are often so Further protection is usually afforded by bracts. termsU are equally applicable to mosses, liverworts Put simply, a bract is a modified leaf protecting the vital for correct identification. and hornworts, but in the reproductive organs antheridium or archegonium. Perichaetial bracts important differences are apparent. Unlike the are found below the perianth and, in certain genera, mosses, capsule and seta characters are rarely such as Jungermannia and Solenostoma, a short used for identification of liverworts, but associated fleshy tube called a perigynium may also develop reproductive structures are important and have their below the female bracts and/or perianth. Archegonium own names. In this article I shall try to demystify Locating male inflorescences can often be the n Perianth and other structures (Scapania). S. Pilkington some of the terms used in current accounts of key to determining if a liverwort is dioicous (separate the British liverwort flora, including Paton (1999) male and female plants) or monoicous, with male self-fertilization, antheridia and archegonia mature and Smith (1990). For superb photographs and and female sexual organs borne on the same plant. at different times in some monoicous species, and illustrations I would strongly recommend Malcolm Many monoicous leafy liverworts are autoicous, thus individual plants may appear to be dioicous at & Malcolm (2006). bearing spatially distinct male and female branches certain times of year. With the exception of the large Like mosses, liverworts reproduce sexually on the same plant, but some species are paroicous, thalloid liverworts in the Marchantiaceae family, through the production of male and female sexual where the antheridia are hidden in the axils of antheridia and archegonia are usually immersed in organs often associated with specialized leaves male (perigonial) bracts just below the female the thallus. After fertilization, the capsule starts to (bracts) in what is termed an inflorescence on the inflorescence. Unlike mosses, liverworts are rarely develop and is protected by an involucre, a tube green parts of the shoot or thallus (gametophyte). synoicous, where archegonia and antheridia are serving the same function as the perianth in leafy The male inflorescence is known as a perigonium; Antheridium mixed in the same inflorescence. However, closer liverworts. Characters such as the presence of teeth the female is the perichaetium. The antheridium inspection will always reveal the differences. at the mouth of the involucre are sometimes used in (male organ) produces sperm cells which fertilize the identification. When mature, the capsule is usually archegonium (female organ), prompting develop- thalloid liverworts raised by the seta above the thallus, although in ment of the sporophyte (the capsule, seta and It is normally relatively straightforward to tell if a ephemeral genera, e.g. Riccia, the capsules may associated structures). The antheridium looks like a n A generalized antheridium and archegonium. thalloid liverwort has reproductive structures and remain totally immersed in the thallus until spores small ovoid pouch with a short stalk and is normally S. Pilkington if it is dioicous or monoicous. However, to avoid are released through disintegration of thallus tissue.
44 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 45 Beginner’sCorner Beginner’s corner
found in the axil of a modified leaf (bract). The archegonium is flask-shaped with a long neck and Capsule Liverwort swollen base which contains an egg cell. Between species, the appearance of the individual sexual Seta organs does not differ much.
Leafy liverworts reproductive structures – Perianth When fertile, most British leafy liverworts develop a perianth, a tube-like structure formed by the fusion of a few leaves that surrounds and protects Female (perichaetial) demystifying the jargon the developing capsule. Perianths are typically bract longer-lived and more distinctive than the capsules themselves, which may take up to a year to develop. Size, shape and other characters vary between nderstanding the terms used to In this edition of Beginner’s Corner Sharon species and can be important diagnostic features. For example, the characteristic ‘star-like’ perianths describe liverwort structures and Pilkington turns her attention to the Leafy shoot knowing what they look like and of the Lejeuneaceae are produced by folds in the where to find them is fundamental confusing and difficult subject of liverwort perianth. to identification. Many bryological reproductive structures that are often so Further protection is usually afforded by bracts. termsU are equally applicable to mosses, liverworts Put simply, a bract is a modified leaf protecting the vital for correct identification. and hornworts, but in the reproductive organs antheridium or archegonium. Perichaetial bracts important differences are apparent. Unlike the are found below the perianth and, in certain genera, mosses, capsule and seta characters are rarely such as Jungermannia and Solenostoma, a short used for identification of liverworts, but associated fleshy tube called a perigynium may also develop reproductive structures are important and have their below the female bracts and/or perianth. Archegonium own names. In this article I shall try to demystify Locating male inflorescences can often be the n Perianth and other structures (Scapania). S. Pilkington some of the terms used in current accounts of key to determining if a liverwort is dioicous (separate the British liverwort flora, including Paton (1999) male and female plants) or monoicous, with male self-fertilization, antheridia and archegonia mature and Smith (1990). For superb photographs and and female sexual organs borne on the same plant. at different times in some monoicous species, and illustrations I would strongly recommend Malcolm Many monoicous leafy liverworts are autoicous, thus individual plants may appear to be dioicous at & Malcolm (2006). bearing spatially distinct male and female branches certain times of year. With the exception of the large Like mosses, liverworts reproduce sexually on the same plant, but some species are paroicous, thalloid liverworts in the Marchantiaceae family, through the production of male and female sexual where the antheridia are hidden in the axils of antheridia and archegonia are usually immersed in organs often associated with specialized leaves male (perigonial) bracts just below the female the thallus. After fertilization, the capsule starts to (bracts) in what is termed an inflorescence on the inflorescence. Unlike mosses, liverworts are rarely develop and is protected by an involucre, a tube green parts of the shoot or thallus (gametophyte). synoicous, where archegonia and antheridia are serving the same function as the perianth in leafy The male inflorescence is known as a perigonium; Antheridium mixed in the same inflorescence. However, closer liverworts. Characters such as the presence of teeth the female is the perichaetium. The antheridium inspection will always reveal the differences. at the mouth of the involucre are sometimes used in (male organ) produces sperm cells which fertilize the identification. When mature, the capsule is usually archegonium (female organ), prompting develop- thalloid liverworts raised by the seta above the thallus, although in ment of the sporophyte (the capsule, seta and It is normally relatively straightforward to tell if a ephemeral genera, e.g. Riccia, the capsules may associated structures). The antheridium looks like a n A generalized antheridium and archegonium. thalloid liverwort has reproductive structures and remain totally immersed in the thallus until spores small ovoid pouch with a short stalk and is normally S. Pilkington if it is dioicous or monoicous. However, to avoid are released through disintegration of thallus tissue.
44 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 45 Beginner’s corner Beginner’s corner
Male plant Female plant In Pellia epiphylla (a monoicous liverwort), the also refer to perianths in thalloid liverworts so the archegonia (and ultimately the capsules) are borne structural distinction can seem unclear. towards the apex of a main thallus, with many Many thalloid liverworts also reproduce asexually Perianth antheridia immersed in small warts/papillae on the via gemmae – the most familiar example is probably midrib behind. The shape of the sexual organs is Lunularia cruciata, named for the crescent-like similar to those of the leafy liverworts. gemma cups it always bears in abundance. When mature, some antheridia are brightly coloured, as in the case of certain species of Sharon Pilkington Fossombronia, which are orange. e [email protected] Leafy Liverworts in the Marchantiaceae – such as shoot Male References inflorescence Marchantia polymorpha, Conocephalum conicum Malcolm, W.M. & Malcolm, N. (2006). Mosses and Other Bryo- and Preissia quadrata – have specialized sexual v A dioicous leafy liverwort phytes, an illustrated glossary. Nelson: Micro-Optics Press. branches on the thallus called receptacles. Rather (Frullania dilatata). S. Pilkington Paton, J.A. (1999). The Liverwort Flora of the British Isles confusingly, the developing sporophyte is protect- Colchester: Harley Books ed not by an involucre, but by a pseudoperianth, Smith, A.J.E. (1990). The Liverworts of Britain and Ireland. though its function is the same. Some authors Cambridge: Cambridge University Press.
Immature Perianth capsule
v A generalized autoicous leafy liverwort (Lejeuneaceae). S. Pilkington
Shoot , A thalloid liverwort, Marchantia polymorpha, Female Antheridial with receptacles and branch tubules Involucre gemma cups. S. Pilkington , A generalized paroicous leafy liverwort. S. Pilkington
Receptacle Male branch Perianth
Young involucre Antheridium Antheridium n A thalloid liverwort, Pellia epiphylla, demonstrating monoicous characters. S. Pilkington
Female (perichaetial) Male (perigonial) Thallus bract bract Gemma cups
46 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 47 Beginner’s corner Beginner’s corner
Male plant Female plant In Pellia epiphylla (a monoicous liverwort), the also refer to perianths in thalloid liverworts so the archegonia (and ultimately the capsules) are borne structural distinction can seem unclear. towards the apex of a main thallus, with many Many thalloid liverworts also reproduce asexually Perianth antheridia immersed in small warts/papillae on the via gemmae – the most familiar example is probably midrib behind. The shape of the sexual organs is Lunularia cruciata, named for the crescent-like similar to those of the leafy liverworts. gemma cups it always bears in abundance. When mature, some antheridia are brightly coloured, as in the case of certain species of Sharon Pilkington Fossombronia, which are orange. e [email protected] Leafy Liverworts in the Marchantiaceae – such as shoot Male References inflorescence Marchantia polymorpha, Conocephalum conicum Malcolm, W.M. & Malcolm, N. (2006). Mosses and Other Bryo- and Preissia quadrata – have specialized sexual v A dioicous leafy liverwort phytes, an illustrated glossary. Nelson: Micro-Optics Press. branches on the thallus called receptacles. Rather (Frullania dilatata). S. Pilkington Paton, J.A. (1999). The Liverwort Flora of the British Isles confusingly, the developing sporophyte is protect- Colchester: Harley Books ed not by an involucre, but by a pseudoperianth, Smith, A.J.E. (1990). The Liverworts of Britain and Ireland. though its function is the same. Some authors Cambridge: Cambridge University Press.
Immature Perianth capsule v A generalized autoicous leafy liverwort (Lejeuneaceae). S. Pilkington
Shoot , A thalloid liverwort, Marchantia polymorpha, Female Antheridial with receptacles and branch tubules Involucre gemma cups. S. Pilkington , A generalized paroicous leafy liverwort. S. Pilkington
Receptacle Male branch Perianth
Young involucre Antheridium Antheridium n A thalloid liverwort, Pellia epiphylla, demonstrating monoicous characters. S. Pilkington
Female (perichaetial) Male (perigonial) Thallus bract bract Gemma cups
46 FieldBryology No108 | Nov12 FieldBryology No108 | Nov12 47