Orthotrichum lyellii
Scientific classification
Kingdom:	Plantae
Division:	Bryophyta
Class:	Bryopsida
Subclass:	Bryidae
Order:	Orthotrichales
Family:	Orthotrichaceae
Genus:	Orthotrichum
Species:	O. lyellii
Binomial name
Orthotrichum lyellii W. J. Hooker & T. Taylor
Synonyms
Pulvigera lyellii (Hook. & Taylor) Plášek, Sawicki & Ochyra

Orthotrichum lyellii, also known as Lyell's bristle moss, ^[1] is a species of acrocarpous moss belonging to the family Orthotrichaceae. ^{[1] [2]} O. lyellii can be found throughout western North America and Europe. ^{[3] [4]} It is found most commonly growing epiphytically on a variety of trees, and less commonly on rocks or boulder substrates. ^[5]

Description

Orthotrichum lyellii is generally described as forming green and yellow mats, with loose tufts reaching lengths of 3 to 4 cm forming mound-like structures. ^[5] Its leaves are sharply pointed with a single costa and lanceolate linear leaf morphology, being very slender and reaching lengths of 2.5 to 6.5 mm. ^[6] Tufts can reach lengths ranging from 10 to 13 cm, and often are found lying prostrate to the ground. ^[7] The lamina cells of its leaves are papillose, and the entire leaf surface can often be found dusted with brown asexual propagules ( gemmae) which may help to distinguish it from similar species such as Orthotrichum papillosum. ^{[5] [8]} Pale-brown or brown rhizoids may be found located at the base of the plant, with amount of branching varying but usually minimal. ^[7]

Habitat and distribution

Distribution of Orthotrichum lyellii in North America is primarily restricted to west of the Rocky Mountains, extending from Southeastern Alaska to California. ^[4] It can also be found distributed throughout Europe, descending from the United Kingdom to the Mediterranean area of North Africa and Western Asia. ^{[3] [4]} O. lyellii distribution is concentrated in coastal temperate rainforests lying closer to sea level. ^[5]

O. lyellii grows epiphytically on the surfaces of tree trunks and branches; they are more frequently found growing on deciduous trees such as maple, alder and oak, and less commonly on coniferous trees such as spruce and hemlock. ^{[5] [4]} They can also be found on the rocks or boulders located beneath said trees, although the frequency of this is low. ^{[5] [9]}

Reproduction

Unique to O. lyellii within its genus is its dioicous sexual condition, meaning it bears its archegonia and antheridia on different plants. ^{[5] [4]} The male plants can often be identified by their smaller size and are often found as tufts located near female plants. ^{[10] [6]} Another distinctive feature of the male plants is the conspicuous bulb-like branches that harbour its reproductive gametophores. ^[4]

The sporophytic stage is characterized by rare, slightly exserted capsules that are often immersed in the perichaetial leaves. ^{[5] [4]} The sporangia is distinct with 8 ribs that may run either one half or the entire length of the sporangia. ^[6] Like most mosses belonging to the Bryopsida class, O. lyellii has white arthrodontous peristome teeth, with 16 teeth being located in both the exostome and endostome. ^[5] Similar to many mosses of the Orthotrichum genus, the calyptra is hairy with straight hairs running its length, often pointed towards its tip. ^[4]

References