<国立科博専報>青森県におけるオニヤブソテツ, イワイタチシダ, ヤマイタチシダの生殖型と分布 A Note on the Reproductive Type and the Distribution of Cyrtomium falcatum, s.l., Dryopteris varia var. saxifraga, and var. setosa in Aomori Prefecture, Japan
Cyrtomium falcatum (L.f.) PR. (s.l.), Dryopteris varia var. saxifrage (H. ITO) H. OHBA and var. setosa (THUNB.) OHWI comprise the taxonomically most difficult fern group in Japan. To clearify the sexual situations of these taxa in Aomori Pref., northern Japan, the field researches and herbarium studies at TNS have been caried out with special reference to the reproductive type and the variation of some morphological characters (i.e. size and shape of spore and stomata, ect.). Forty specimens of Cyrtomium falcatum, s.l. were collected in various places (Fig. 1). This species occurs on the rocks very near the sea. These specimens were divided into two types based on the number of spores in each sporangium; thirty-six specimens were of the sexual type and four specimens of the mixed type which has both the sexual and apogamous type in a sorus (Tab. 1,Fig. 2,and Fig. 3). In the mixed type, ratio of sexual type to apogamous type in a sporangium of each sorus is ca. 7.8 : 1 (Tab. 1). Only a single specimen of the apogamous type was found among herbarium materials. Shape of frond and pinna (Fig. 5), shape and size of spore, and size of stomata (Fig. 4) of both types were observed and measured. Distribution map of both types (Fig. 6) were presented based on the specimens collected in the present work and the specimens deposited in TNS. Thirty-one specimens of Dryopteris varia group were also collected in various places (Fig. 1). These specimens were divided into two types based on the number of spores in a sporangium; eighteen specimens of the sexual type were determined to be Dryopteris varia var. saxifrage (Fig. 9), and thirteen specimens of the apogamous type to be var. setosa (Fig. 9). Variation in the shape and size of stomata and spore were observed and measured for both types (Fig. 7). These two taxa are closely related each other in the size and shape of frond, lamina and indusium, color of scale, and position of sorus, but clearly different in the scales at the upper part of stipe (Fig. 8). Var. saxifraga grows on slope on the edge of forests and on the wet rocks along streams, and var. setosa on slope of forests near small streams, and on wet rocks in forests. These two taxa are growing sympartrically in the northernmost place of Aomori Pref. Distribution map (Fig. 9) of var. saxifraga and var. setosa were presented based on the specimens collected in the present work and those deposited in TNS.