XIV] 



THE GAMETANGIA 



285 



For the latter the adoption of the mycorhizic habit has made such Hfe pos- 

 sible. These considerations indicate that the mycorhizic type of prothallus 

 is not so far removed from that of other Filicales as it would appear to be 

 at first sight. (See Lang, PJiil. Trans. Vol. 190, 1898, p. 187.) 



The Gametangia 



The male and female gametangia resemble the sporangia in the fact that 

 the gametes like the spores are borne internally, and are covered over till 

 maturity by a wall composed of one or more layers of cells. Their structure 

 may be held to be a general consequence of the fact that the plants which 

 bear them are normally exposed to the air during development, and since the 

 gametes are primordial cells they must be protected. Like the sporangia, the 

 gametangia may in some cases be deeply sunk in the parent tissue, in others 

 they may project in more or less marked degree. It will be seen later that 

 the analogies between gametangia and sporangia may be followed into still 

 further detail ; but first the gametangia themselves must be described and 

 compared. 



The antheridia and archegonia of Matteuccia Striithiopteris, which are 

 essentially similar to those of Dryopteris, will serve 

 as average examples for ordinary Leptosporangiate 

 Ferns (see Chapter i, Fig. 20). The antheridium ori- 

 ginates as a hemispherical protrusion from a single 

 prothallial cell, which is then partitioned offby a trans- 

 verse or somewhat oblique wall. It contains cytoplasm 

 with chlorophyll, and a large central nucleus. Its first 

 segmentation is by a funnel-shaped wall, the base of 

 which strikes the basal wall of the antheridium (Fig. 

 276, A)\ sometimes, however, this wall does not reach 

 down to the basal wall, but taking a more or less 

 convex course it cuts oft" a discoid stalk from the 

 distal head {B). The latter then divides by an hemi- 

 spherical wall nearly concentric with the outer wall. 

 This cuts off an external cell, forming the antheridial 

 wall into which all the chloroplasts pass, from an 

 inner colourless cell. The latter is the mother-cell of 

 the spermatozoids. The cell of the antheridial wall 

 undergoes a further ring-like division, cutting off a 

 cap-cell at the top. The young antheridium then 

 consists of four cells, viz. the central mother-cell, two 

 ring-shaped cells, and a discoid terminal cell. The 

 cells of the wall have meagre cell-contents except the chloroplasts, which 



Fig. 276. Antheridium of 

 Matteuccia Striithiopteris, 

 after Campbell. A, B = 

 young antheridia in vertical 

 section, to show segmenta- 

 tion. C= adult antheridi- 

 um with 2 I spermatocytes 

 in section. ( x 200.) 



