Arctoa (2000) 9: 151-154 OBSERVATIONS ON STEM SURFACE ANATOMY IN CLIMACIUM AND PLEUROZIOPSIS (CLIMACIACEAE: MUSCI) Î ÑÒÐÎÅÍÈÈ ÏÎÂÅÐÕÍÎÑÒÈ ÑÒÅÁËß CLIMACIUM È PLEUROZIOPSIS (CLIMACIACEAE: MUSCI) DANIEL H. NORRIS1 & MICHAEL S. IGNATOV2 ÄÀÍÈÝËÜ Ã. ÍÎÐÐÈÑ1 & ÌÈÕÀÈË Ñ. ÈÃÍÀÒÎÂ2 Abstract Pleuroziopsis was segregated from Climaciaceae into a separate monotypic family Pleuroziopsidaceae by Ireland (1968). According to Ireland, the most important and unique characteristic of Pleuroziopsis is a fluting of the stem by streaks of stem lamellae. However, this pattern of stem fluting is shown to be shared with the genus Climacium, so Pleuroziopsis is returned to Climaciaceae. Ðåçþìå Pleuroziopsis áûë âûäåëåí èç ñåìåéñòâà Climaciaceae â ñàìîñòîÿòåëüíîå ìîíîòèïíîå ñåìåéñòâî Pleuroziopsidaceae (Ireland, 1968). Îñíîâàíèåì äëÿ ýòîãî ïîñëóæèëî íàëè÷èå ïðîäîëüíûõ ‘ñòåáëåâûõ ïëàñòèí’, ñòðóêòóðû, êàê ñ÷èòàë Àéðåëàíä, íå èìåþùåé ãîìîëîãîâ. Îäíàêî, äàííîå èññëåäîâàíèå âûÿâèëî, ÷òî ñòðóêòóðà ïîâåðõíîñòè ñòåáëÿ ó Climacium è Pleuroziopsis ïðèíöèïèàëüíî ñõîäíà, òàê ÷òî ïîñëåäíèé ðîä ïðåäëàãàåòñÿ âåðíóòü â Climaciaceae. Many years ago, I (DHN) found myself with anatomy was first thought to allow easy sorting R. Ochyra, Krakow, in several very profitable dis- according to the observations of Ireland (1968). I cussions on paraphyllial arrangement in Hyp- (DHN) removed the leaves from both the stem nobryalean mosses. These discussions led in sub- and rhizome material of the two species. At that sequent years to careful observation of the pat- point, the cloaking of rhizoids was so dense as to terns of paraphyllial insertion of moss stems. A require plucking of those rhizoids with fine-point recent trip by DHN to Alaska afforded oppor- forceps. It was with great surprise that we found tunity to study freshly collected material from the denuded stems (split longitudinally to allow a population of Climacium dendroides (Hedw.) increased transparency) to be essentially identi- Web. & Mohr mixed with Pleuroziopsis ruthen- cal in overall patterns. Both species have closely ica (Weinm.) Kindb. ex Brid. It might be noted placed and well-demarcated uniseriate (1-)2-3- in this regard that the Alaskan collection of Pleu- stratose longitudinal streaks on the stem. When roziopsis seems to represent a westward exten- the denuded stems of the two plants are lightly sion of the species on the Alaskan mainland. Data scraped with a razor blade we find almost identi- on this collection is: Alaska: 60°26’N X cal uniseriate streaks of laterally enlarged short 145°06’W: On moist, diffusely lit soil of creek cells on the stem surface (Figs. 1-12). bank in forest of Populus and Picea sitchensis Traditionally, Pleuroziopsis was placed in along Saddlebag Lake Trail, Chugach National Climaciaceae, because of dendroid plants, simi- Forest east of Cordova, Elev. 0-200 m., D. H. lar leaf structure and laminal areolation, and Norris 96798, 24 July 1999 (H). presence of paraphyllia (e. g. Brotherus, 1925). This collection of Pleuroziopsis had its sto- Ireland (1968) was the first who found inappro- lons so tightly interwoven with those of Climaci- priate the application of term paraphyllia to Pleu- um dendroides that it became necessary to clean roziopsis, and reinterpreted them as rhizoids (cf. the specimen by following the pattern of inter- Fig. 1 in Ireland, 1968). Longitudinal rows of cells growth. Careful monitoring of the stem surface along the stem were understood by him as “stem 1 – University Herbarium, University of California, Berkeley 94720 & Botanical Museum, University of Helsinki, Box 47, SF 00014, Helsinki, Finland 2 – Main Botanical Garden of Russian Academy of Sciences, Botanicheskaya 4, Moscow 127276, Russia 152 DANIEL H. NORRIS & MICHAEL S. IGNATOV 200 μm 100 μm 1 4 50 μm 5 2 6 3 Figs. 1-7. 1-3: Climacium dendroides (Hedw.) Web. et Mohr (from Alaska, Norris 96798a): Stem surface after removal of most of rhiz- 7 oids (1-2) and transverse stem section (3). 4-7. Pleuroziopsis ruthenica (Weinm.) Kindb. ex Britt. (from from Alaska, Norris 96798): Stem surface (4) and transverse stem sections (5-7). Scale bars: 200 μm for 1; 100 μm for 2-4, 7; 50 μm for 5-6. Observations on stem surface anatomy in Climacium and Pleuroziopsis 153 8 9 10 11 Figs. 8-12. SEM photographs of stem surface. 8 & 10: Climacium dendroides (Hedw.) Web. et Mohr (from Rus- sia, Vladimir Prov., Nazarov 259, MW): 8 – intact stem surface, with dense rhizoid cover; 10 – stem after removal of most of rhizoids, showing micronemata initials with rhiz- oids; 9, 11-12: Pleuroziopsis ruthenica (Weinm.) Kindb. ex Britt. (from Russia, Primorsky Territory, Makarov, X.1972 , MHA): 9, 11 – stem with inflated micronemata initials (‘stem lamellae’); 12 – same with micronemata. lamellae”, a structure without any homology in the other groups of mosses, which allow to segregate Pleuroziopsis into a separate family. The nearly 12 identical stem pattern of Climacium (Fig. 10) was not found by Ireland apparently due to very dense According to this set of characters, stem struc- “paraphyllia” cover (Fig. 8). In contrast to Cli- tures of Climacium & Pleuroziopsis have more macium, Pleuroziopsis has rather few rhizoids and common character states with rhizoids. This in- much enlarged terminal cell of “lamellae”, which terpretation disagrees only with their green col- are easy to observe (Figs. 9, 11-12). or, apparent in Climacium, and less so in Pleu- The differences between rhizoids and para- roziopsis due to rhizoid rarity. We do not think, phyllia can be summarized as follow: that the presence of chlorophyll is the most important character in this case. The reinter- Character Paraphyllia Rhizoids pretation of Climacium' stem outgrowth as Color green brown, rare colorless rhizoids leads in reward to the more narrow Growth +determined +indetermined definition of paraphyllia as a foliose structure Width at least at base always uniseriate 2- or pluriseriate (i. e. at least 2 cell wide at base), because, as far Transverse +perpendicular oblique as we know, Climacium was the only genus with cell walls totally filamentose paraphyllia. Surface orna- smooth or similar smooth or However, the detail comparison of paraphyl- mentation to that of leaf cells granulose lia and rhizoids are out of scope of this paper. 154 DANIEL H. NORRIS & MICHAEL S. IGNATOV Our main thesis is the principal similarity contrast, they place Pleuroziopsis in an order of the longitudinal streaks in Climacium and Hypnales with a suborder Hypnodendrineae Pleuroziopsis with micronematous initials as (Pterobryellaceae, Hypnodendraceae, Pleurozi- they were described by Koponen (1968) for opsidaceae, and Thamnobryaceae). This treat- Mniaceae. As with the Mniaceae, an initially ment centers upon the sporophyte modifica- long cell of the outer stem cortex forms a series tion in Climacium, including erect cylindric of transverse walls defining a row of a relative- capsule; gradually tapered teeth with nearly ly short cells. Each of such cells may now pro- straight median-line and papillose rather than duce the outgrowths which we interpret as mi- striolate outer teeth below; narrow segments, cronemata: at least some more distal cell walls lack of ciliae, and very low basal membrane. are clearly oblique (cf. Figs. 3, 7). However both The modification of peristome from the basic Climacium and Pleuroziopsis differ from Mni- Hypnoid-type in Pleuroziopsis is much smaller aceae in that the micronemata initials are raised and include only complete reduction of cili- above stem surface, whereas in the latter family, ae. However, the peristome modifications, or rows of micronematous initials remain at the reduction, are known within many families of stem surface level. pleurocarps, but usually do not lead to a fa- The primary aim of this paper is to argue milial segregation (cf. Ignatov & al., 1998). that Ireland’s (1968) distinction of the two fam- In recent discussion (April, 2000), Hedenäs ilies is probably inappropriate. These are two called our attention that such features as the re- plants of temperate and subarctic regions of duced/+complete peristome and the straight/re- the northern hemisphere. It is notable that tru- flexed perichaetial leaves might argue against a ly dendroid (as opposed to frondose1) mosses close relationship between Climacium and Pleu- are represented in this area only by Climacium roziopsis. However, erect perichaetial leaves are of- and Pleuroziopsis, which strengthen the view ten associated with taxa with erect capsules in of their close relationship. families where taxa with curved capsules have re- It is interesting that the exclusion of Pleu- flexed perichaetial leaves (for example, Homal- roziopsis from the Climaciaceae by Ireland othecium and Rhynchostegiella have often straight (1968) has spawned a spate of papers plac- perichaetial leaves and erect capsules, in con- ing the genus quite distant from Climacium. trast to most other species of Brachytheciaceae, Buck & Vitt (1986) recognize Climacium in etc). So, we believe that separation of the family an order Leucodontales with a suborder Cli- Pleuroziopsidaceae from the Climaciaceae is not maciineae (Trachylomataceae & Climaciace- sufficiently demonstrated and we return Pleurozi- ae) which is sister to their Neckerineae. In opsis to its classical position in the Climaciaceae. LITERATURE CITED BROTHERUS, V. F. 1925. Musci. – In Engler, A. & K. IGNATOV, M. S., H. ROBINSON & E. A. IGNATOVA Prantl (eds.) Die Natuerlichen Pflanzenfamilien, ed. 1998. Studies on the exostome of Brachytheciaceae