210 



ORIGIN AND RELATIONSHIPS OF THE EUSPORANGIATAE 



The large, green sporophyte, however (fig. 190, A, sp), never attains complete inde- 

 pendence, as no proper root is developed and it is dependent for its water supply 

 upon the gametophyte. 



In all of the Eusporangiates, the embryo is much later in developing its organs 

 than in the Leptosporangiates, and thus resembles the Bryophytes; moreover, the 

 embryo reaches a very much larger size before it attains its independence. Even 

 after the young sporophyte has developed several roots and leaves, it may still 



Fig. 190. 



A. Gametophyte of Anthoccros sp. with the large 

 sporophyte, sp, attached to it. Upper part 

 of sporophyte is sph't into valves which allow 

 the escape of spores. 

 B, C. Two gametophytes of Marattia douglasii, with 

 attached sporophyte. Sporophyte emerges 

 upon upper side of gametophyte, very much 

 as in Anthoceros, but a root, r, is developed 

 which penetrates lower side of gametophyte 

 and connects the young sporophyte with the 

 earth, g, gametophyte; sp, sporophyte; 

 /, first leaf; r, primary root. 



maintain its connection with the gametophyte and be to a certain extent dependent 

 upon it in a way which forcibly recalls the relation of gametophyte and sporophyte 

 in the mosses. This condition, which furnishes a very strong argument in favor of 

 the primitive nature of the Eusporangiates when compared with the Leptosporan- 

 giates, is especially pronounced among the Ophioglossaceae, where it may even go so 

 far that spores are developed before the connection of gametophyte and sporophyte 

 is finally sundered. 



In the true mosses the sporophyte is exceedingly specialized and shows but a 

 very remote resemblance to that of the Pteridophytes. In Anthoceros, however, the 



Fig. 191. 



Diagrams which show the similarity in form of the very 

 young sporophyte in Anthoceros, A, and Ophioglossum , 

 B. In the former the upper portion becomes an elong- 

 ated capsule within which spores are produced. The 

 shaded portion shows layer of sporogenous tissue sur- 

 rounding central sterile tissue or columella. The 

 zone, w, between capsule and foot, /, is composed of 

 meristematic tissue. In Ophioglossum the upper part 

 of the young sporophyte forms the primary leaf, or 

 cotyledon, cot, which is not sporogenous. The colum- 

 ella of Anthoceros is replaced by the axial vascular 

 bundle, v. &. At the junction of the cotyledon and 

 foot arises the primary root, r, which finally penetrates 

 the foot and enters the ground. 



most highly developed of the horned liverworts, there are a number of very significant 

 structural details that are very strongly reminiscent of the young sporophyte of 

 Ophioglossum moluccanum. In both of these forms the young embryo has a very 

 large foot and a conical upper region (fig. 191). This upper portion in Ophioglossum 

 develops into the cotyledon; in Anthoceros, into the spore-bearing part of the sporo- 

 phyte. Above the foot in Anthoceros there is developed a zone of meristematic 

 tissue by means of which new cells are added to the base of the growing spore- 



