Abstract
The gametophytic generation of Amblovenatum immersum and Christella subpubescens (Thelypteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and reproduction strategies, was studied. For both species, the spore germination was of the Vittaria type and the developmental pattern was of the Drynaria type. Adult gametophytes were cordate and hairy, with unicellular and secretory hairs located in the margins and both the ventral and dorsal surfaces of the prothalli. C. subpubescens has another type of acicular hairs only in the margin of the prothallus. Gametangia were of the normal type described for leptosporangiate ferns. In A. immersum all the gametophytes were female. In C. subpubescens the gametophytes produced at first instance female gametangia and then became bisexual with time. Antheridiogen activity was observed in both species, suggested by the presence of small young ameristic gametophytes with antheridia surrounding well-developed female ones.
Highlights
Our observations of the spores of A. immersum and C. subpubescens are consistent with previous descriptions for both genera (Nayar & Kaur 1971; Holttum 1976, 1977; Smith 1990) on size, shape and ornamentation
The spores of both species germinated around the ninth day, which is within the average germination time of fern spores without photosynthetic pigments (Gabriel y Galán & Prada 2010) and corresponds to the germination times of spores from the same family (Sen 1981)
The germination pattern for both species corresponds to the Vittaria type (Nayar & Kaur 1968, 1971), which is characterized by the first rhizoid and the first prothallial cell emerging perpendicularly one to each other
Summary
Is one of the largest cosmopolitan fern families, with a tropical and subtropical distribution, reaching its greatest diversification in Malaysia (Tigerschiöld 1989). With approximately 900-1000 species (He & Zhang 2012), it is one of the most diverse fern families. There is some controversy in the number of genera in which it is divided since it varies between 5 and 30 (Smith et al 2006). According to the most recent classification it contains 27 genera (PPGI 2016). The classification of the family remains quite controversial due to the high degree of convergence and parallel evolution that its genera present, especially in the morphological characters. There are still unsolved genera such as Christella H.
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