Acta Botanica Croatica, Vol. 1 No. 1, 1925.
Izvorni znanstveni članak
Development and affinities of the Fern Cheilanthes
Ivo Horvat
; Hrvatska
Sažetak
First the development of both generations of the species Cheilanthes odora Web & Berth is described and then, based on these results, the affinités of the genus Cheilanthes with the family Schi-zeaceae are treated.
1. At the beginning the gametophyte grows with its apical cell and then with its central meristem. The membranes of the vegetative cells show a columnar swell (»saülchenförmige Verdickungen«) in its corners and lateral walls. The structure of the sexual organs does not show anything particular. The antheridia opercula cell is undivided. At first the sporophyte i§ covered with hairs, but in an advanced stage its trunk is covered with scales. Its structure is dictyostelic; in the xylem there are besides the tracheids parenchim- cells. In the stele of the petiole the xylems are separated at the base.
The sorus develops into quite a low receptacle in the immediate neighbourhood of the leaf margin and the small number of the sporangia in a definite succession of time and space. The structure of the sorus is that of the Gradatae. The sporangium develops from one cell, which has slightly risen above the level of the: receptacle. The first segment-wall extends from the outer to the inner (basic) periclinal wall of this cell. The Tapetum is normally differentiated, the section of the archespores shows a small spore output. The annulus does not reach the insertion of the stalk nor the differentiated stomium. The spores have no periplasmodion.
2. Certain characteristics in the ontogenesis of the investigated species warrant, in the author’s opinion, conclusions as to the origin and the affinity of the genus Cheilanthes and its near unindusiatae Mixtae. The characteristic swelling in the prothallic cells, as well as the position of the sorus, show a genetic conection with the Schizeaceae. The first segmentation of the sporangia indicates primitiveness and is quite the same as that of the Schizeaceae. The structure of the sorus shows an advance. The gradated development of the investigated fern is a transition from the primitive type of the Schizaeceae to the most derivated ones of the Clieilanthineae to which it is linked through the structure of the ripe sporangium and a small spore output.
Hence these investigations have established the suggested relationship of the genus Cheilanthes as the link between the most primitive and the most derivate unindusiate Marginales.
Ključne riječi
ferns; genus Cheilanthes; development
Hrčak ID:
151650
URI
Datum izdavanja:
31.12.1925.
Posjeta: 927 *