Αρχεία Ημερολογίου για Δεκέμβριος 2022

Δεκέμβριος 29, 2022

How to know and photograph a liverwort

In the Pacific Northwest, there are more than 200 species of liverworts loitering in typically moist habitats. While identification can require microscopic examination, it is possible to get to species in the field or using photographs provided you shoot the right features. This post is intended for anyone who want to figure out their liverworts or wants help from others to do so. It will cover (1) how to recognize a liverwort and (2) how to photograph a liverwort in a way that increases probability of identification to species.

What is a liverwort?

Like mosses and hornworts, a liverwort is a plant where the life cycle is dominated by a persistent photosynthetic gametophyte that hosts a relatively short-lived and nutritionally dependant sporophyte (spore-bearing) phase. Liverworts can be leafy (see photos of Plagiochila porelloides and Porella navicularis) like mosses, but the leaves are always a single cell thick and they lack a mid vein. The leaves if liverworts also tend to be inserted in two ranks, 1 on each side of the stem, and frequently show a smaller leaf on the underside of the stem. Leaves of liverworts are frequently lobed, with those lobes varying in number and being equal, unequal, pointed, rounded and so forth. Mosses, by contrast have unlobed leaves that typically have a mid vein (“costa”) that consequently makes them more than one cell thick. Furthermore, moss leaves typically show leaves arranged all around the stem and of similar form and size.

The other group of liverworts is thalloid, having a continuous, frequently branching, flattened mass of photosynthetic tissues (see photos of Pellia neesiana and Marchantia polymorpha). What makes these liverworts? When sporophytes are present, their ovoid capsules open by longitudinal dehiscence, just as they do when present in the leafy liverworts. Within the capsules of both thalloid and leafy liverworts are odd little spring-like cells called elaters that expand and contract in response to moisture differences. Moss sporophytes by contrast lack elaters and open usually by a lid at their apices. Hornwort sporophytes have “pseudoelater” (that won’t help much in the field), and their exceedingly elongate capsules open by extensive longitudinal dehiscense lines (see Anthoceros fusiformis). The photosynthetic phases of both leafy and thalloid liverworts have cells that contain oil bodies, a feature that distinguishes this group from both mosses and hornworts.

How to photograph a liverwort

I often encounter great photos of liverworts on iNaturalist, but because they are limited to a single shot from a single perspective showing a single aspect of the plant, they are hard to interpret. By taking 15-30 extra seconds to photograph a few other features, you can take a mysterious liverwort and make it so that you and/or others can identify it at least to genus and often to species. The following shots are an ideal sequence:

(1) Habitat-a shot showing the liverwort in its environment— eg. Growing on a tree or along a soil bank. You can also just write this down in your observation notes that you upload with your photos
(2) Habit- a shot showing the whole plant with features like branching, orientation (is it upright? creeping? prostrate? Are sporophytes present?
(3) Shot of the upper side of the leafy plant or thallus to show leaf arrangement and general shape, presence and absence of pores et al. Could also possibly show developing antheridia, archegonia and sporophytes.
(4) Shot of the underside of the leafy plant or thallus. This will show features like underleaves, underlobes of lateral leaves, rhizoids, possibly developing antheridia, archegonia and sporophytes.
(5) Detail shot of leaf margin or upper thallus— the presence, absence, shape and relative size of lobes and teeth for leafy liverworts. For thalloid liverworts, this will show the presence and absence of pores and scales.
(6) If sporophytes are present, try and photograph them from above and below to show their relative size and surrounding leaves and structures (if present).

Obviously, shooting liverworts can be challenging on account of their size, but you can capture most of these things with a cell phone camera and magnifying glass/hand lens in the worst case scenario. I find picking a small sprig and holding it up to the sun or bright sky is particularly helpful in seeing finer details like leaf details (see photo of Ptilidium californicum).

Posted on Δεκέμβριος 29, 2022 0827 ΜΜ by rambryum rambryum | 2σχόλια | Αφήστε ένα σχόλιο

Δεκέμβριος 31, 2022

Regarding Pulvigera/Orthotrichum lyellii in the Pacific Northwest

One of the most common epiphytic mosses in the PNW is something that was traditionally called Orthotrichum lyellii. It immediately announces itself on account of its longish, erectish, unbranched-ish shoots, short sporophytes with hairy caps. When a group of bryologists in Spain took a closer look at herbarium samples of purported O. lyellii, they found collections from western North America were distinct.

The type specimen of Orthotrichum lyellii seems to have been collected on a tree in the "New Forest, Hants" (present day southern England) by a young Charles Lyell long before the publication of his three volume Principles of Geology. The material was treated as a new species by WIlliam Jackson Hooker (First Director of Kew Gardens, father of Joseph Dalton Hooker) and Thomas Taylor in their Muscologia Brittanica. It is notable for having seperate male and female plants ("Dioicous") and little asexual propagules on the leaves.

The problem that Lara et al. addressed was that the material from the west coast of North America, while having seperate male and female plants, lacked those asexual propagules on the leaves. They expanded on the concept of the genus Pulvigera to include all dioicous species previously treated as Orthotrichum. After some molecular work and morphological characterization, it turned out that Orthotrichum lyellii does not occur in the Pacific Northwest, with the closest records being in California. That material, with its asexual propagules is now referred to as Pulvigera lyellii.

What does occur in Oregon, Washington and British Columbia turned out to be two morphologically distinct species: Pulvigera pringlei and Pulvigera papillosa. Below I copy and paste the couplet from Lara et al.'s revised key to the genus. That in turn is followed by links to examples of iNat observations of these species. While some of the characters are microscopic, the size and form of the sporophyte is something that can be seen in the field and caught on film.

Vaginula densely hairy; capsules emergent to short exserted, seta 1.75–3.40 mm long; operculum plane
or slightly plane-convex, with a broad reddish-orange basal rim; external side of teeth with papillae and
longitudinal lines in the upper part; endostome with a faint connective membrane, no or faintly coloured;
spores finely papillose .......................................................................................................................P. pringlei
Vaginula sparsely hairy; capsules almost immersed to widely emergent, seta 1.0–1.5 mm long; operculum
strongly convex, almost dome-shaped, rarely plane-convex, with a little conspicuous yellowish to pale
orange basal rim; external side of teeth coarsely papillose in the upper part; endostome with a showy
orange connective membrane; spores coarsely papillose ............................................................. P. papillosa

Example of Pulvigera pringlei. -note long seta
Example of Pulvigera papillosa -note short seta and nearly immersed capsule, convex operculum
Example of male plant of Pulvigera, which cannot be IDed to species unless growing in close proximity to a female plant bearing sporophytes. Note bulb-like growths where antheridia (sperm-beaaring organs) are engulfed in leaves
Example of actual Pulvigera lyellii -- note the abundant asexual propagules growing on the leaf surface

Posted on Δεκέμβριος 31, 2022 0201 ΠΜ by rambryum rambryum | 10σχόλια | Αφήστε ένα σχόλιο

Homebrew Resources for Bryology

Yesterday I found myself lingering in the stool-softener section of the pharmacy trying to find the product that contained docusate sodium. Turns out this is the second product in the laxative aisle that is helpful for looking at bryophytes. Many of these tools and techniques are described in two great resources for home bryology:

(1) @david1945wagner 's Tools, Tricks & Techniques section of his website. Here you can get tips for simplifying microscopy, microscope photography, specimen hydration (stool softener!, special needlepoint applicator bottles), staining, slide preservation and more. Dr. Wagner has also put out two really illustrative videos on making herbarium packets and botanical illustration.

(2) Janice Glime's Lab Techniques chapter (cowritten with David Wagner) from her fantastic five volume open access Bryophyte Ecology book. This chapter gets into the nitty gritty of specimen cleaning, staining, mounting and preserving for a variety of uses. This is where you can learn about

  • Cleaning specimens: I use a cheap ultrasonic bath intended for jewelry cleaning
  • Staining and Clearing bryophytes (eg. Methylene Blue, a readily available fish medication, can be used for staining sphagnum and spores, KOH for clearing and staining leaves)
  • How to section (freehand with drug store razor blades)
  • Microscope "hacks"

The one technique not mentioned in these two resources that I find very useful is another product from the laxative aisle-- Polyethylene Glycol 3350 (PEG). I learnt about this in @mccuneb & Martin Hutten's Common Mosses of Western Oregon and Washington book. The use of PEG can feel illicit on account of it being a fine white powder that you put on glass and hold over a flame, but it is really helpful for making sections of tiny or delicate leaves. I simply put my leaves or shoots or sporophytes on a glass slide, cover it with the dry PEG granules and then hold a lighter under the slide until the granules melt and surround my specimen. The slide is then left to cool for about a minute, leaving me with an "embedded" specimen without the trouble of parafin and dehydration. The trimmed specimen block is then ready for sectioning.

Bulk Sectioning of Bryophytes
It is crude, but here is a video demonstrating my bulk sectioning technique. It is one way to get good stem and leaf cross sections, best applied when positional accuracy is of no great consequence.

Posted on Δεκέμβριος 31, 2022 0503 ΜΜ by rambryum rambryum | 10σχόλια | Αφήστε ένα σχόλιο