LIVERWORTS - FRULLANIACEAE

This family of liverworts comprises four genera: Frullania accounts for nearly 800 species, Jubula has 15, whilst Steerea and Neohattoria are both monotypic. The plants have a worldwide distribution and are especially common in tropical and subtropical regions but rare in frigid climates. Most are epiphytes growing on trunks and branches of trees and shrubs. Typically, they are tolerant of desiccation and high illumination, but Jubula species are confined largely to damp shaded rock surfaces.

[Summary yet to be added]

Frullania Raddi

The 800 or so species occur as epiphytes in tropical and subtropical regions on trunks and branches of trees, and also on cliffs and rocks. They persist on the bark of fallen trees. Most are a deep madder-red colour.

Epiphytic plants on trees were suspected as agents of contact dermatitis by Spillman (1921). The early literature was reviewed by Schulmann & Détouillon (1932). Le Coulant & Lopes (1956, 1960) incriminated Frullania and lichens in woodcutter's eczema in France, whilst Bancons (1966) detailed the findings in 75 cases. This investigation was subsequently extended by Le Coulant et al. (1966) and by Bancons & Maleville (1967). Mitchell et al. (1969) described 7 cases of Frullania dermatitis from western Canada and 70 additional cases have since been observed from that area (Mitchell JC 1975 — unpublished observation). Other cases have been observed in France (Graciansky & Taieb 1966, Foussereau et al. 1971), and Oregon, USA (Storrs & Mitchell 1975).

Contact dermatitis from Frullania species affects the exposed skin surfaces of forest workers. We have not commonly seen the involvement of the genital region which was emphasised by Le Coulant et al. (1966). Differences in climate and hence in habits of dress may explain the varied distribution patterns. Canadian workers wear rainwear suitable for a cold and wet climate. Workers may become sensitised after only a few weeks or after many years in forest-work. The dermatitis appears within a day or two of contacting vegetation and clears within a few weeks after leaving such work. Attacks are more severe in wet weather and widespread dermatitis can occur if the clothing is wetted by rain. Concomitant contact sensitivity to the fungi of lichens has been observed in 25 of 75 patients (Mitchell et al. 1969). Weakly sensitised workers can usually continue in forest work, but recurrent dermatitis occurs. Strongly sensitised workers are obliged to leave forest work. Cross-sensitivity to other plants, notably to members of the Compositae and Magnoliaceae, is observed (Mitchell et al. 1970, Mitchell & Dupuis 1971, Mitchell 1975c).

Hardening has not been observed in Canadian cases but Le Coulant et al. (1966) produced hyposensitisation in 70% of their cases by repeated application of the plant to the skin. The Canadian cases included a geologist and a gardener, but the great majority have been workers employed in forest industries, notably fallers (those who fell trees). Le Coulant et al. (1966) observed dermatitis most commonly in cultivators, and in lumber-jacks, pruners, forest rangers, wood merchants, truck drivers (who transport wood with the bark on it), saw-mill workers, carpenters, coopers, resin harvesters, cabinet makers, and persons making wooden matches. They found that the allergen of Frullania penetrates into the bark and outer wood of trees, thus contaminating the lumber. The Canadian cases have not included any sawmill workers, and are mostly confined to those who handle the bark of trees. In the Bordeaux area of France, Frullania grows commonly on oak (Quercus, fam. Fagaceae), chestnut (Castanea, fam. Fagaceae), poplar (Populus, fam. Salicaceae), and beeches (Fagus, fam. Fagaceae). In Canada, cedar (Thuja, fam. Cupressaceae), hemlock (Tsuga, fam. Pinaceae), fir (?Picea, fam. Pinaceae), and spruce (Picea, fam. Pinaceae) are among those trees which support the growth of Frullania. These liverworts are often found growing abundantly on shrubs in the understorey of forest areas of coastal British Columbia, Canada. Members of the genera Vaccinium and Menziesia often have large quantities of Frullania growing upon them, and fragments readily break loose and attach themselves to clothing. Terms such as oak dermatitis (France), cedar poisoning (Canada), and spruce dermatitis (Oregon), erroneously applied to Frullania dermatitis reflect the regional differences in habitat. Cedar poisoning should not be confused with dermatitis arising from contact with the heartwood of cedar (see Thuja, fam. Cupressaceae).

In view of the relatively common occurrence of Frullania dermatitis in France and Canada, it seems likely that the disorder goes unrecognised in some other forest areas.

Frullania tamarisci (L.) Dumort.

[syn. Jungermannia tamarisci L.]

This species yields an allergenic sesquiterpene lactone (Knoche et al. 1969, Perold et al. 1972). This species was also studied by Connolly & Thornton (1973). As in the case of sesquiterpene lactones found in members of the Compositae, the principal immunochemical requirement for contact allergenicity is the presence of an α-methylene-γ-butyrolactone ring on the molecule (Mitchell et al. 1970, 1972a). Only one of 12 Frullania species tested was devoid of eliciting activity. The α-methylene-γ-butyrolactone ring is also responsible for cytotoxicity in this class of compounds (Kupchan 1970, Kupchan et al. 1970).

References

• Bancons F, Maleville J (1967) Dermite des bûcherons. Rôle du Frullania. [Loggers' dermatitis. Role of Frullania]. Archives des Maladies Professionnelles, de Médecin du Travail et de Sécurité Sociale 28(3): 407-410
• Le Coulant P, Lopes G (1956) Allergie aux lichens; recherches experimentales preliminaires; extraction d'un allergene à pouvoir antibiotique probable. [Allergy to lichens; preliminary experimental research; extraction of an allergen with probable antibiotic effect]. Journal de Médécine de Bordeaux et du Sud-Ouest 133(9): 869-872
• Le Coulant P, Lopes G (1960) Rôle pathogène des muscinées-hépatiques dans les industries du bois. [Pathogenic role of liverworts in the wood industries]. Archives des Maladies Professionnelles, de Médecine du Travail et de Sécurité Sociale 21(6): 374-376
• [Others yet to be added. Details available on request]

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