THE BRYOPHYTA: HEPATICAE, THE LIVERWORTS 405 



and since sucrose is secreted by both antheridia and archegonia it has been 

 suggested that a form of " insect polHnation " may occur in Marchantia. 



The Archegoniophore 



The archegoniophore is similar in general structure to the antheridiophore. 

 It is made up of a stalk, which is generally longer than that of the antheridio- 

 phore, and a terminal disc, which is also branch-like (Fig. 388). The 

 growing apices of these branches, however, turn downwards and inwards 

 towards the stalk so that their positions are marked by deep indentations 

 in the disc. The tissue between these growing points projects as long 

 finger-shaped processes, like the ribs of an umbrella. The archegonia are 

 formed in small triangular patches near each of the down-turned apices. 

 Each patch is surrounded by an involucral membrane, which is developed 

 from the edges of the ribs and hangs down vertically to protect the developing 

 archegonia. Some twelve to sixteen archegonia are produced in each of 

 these enclosures, and develop in succession from the outside inwards (Fig. 

 389). Their development is more or less similar to that in Pellia, and it is 

 unnecessary for us to consider it in detail. There is, however, one difference, 

 that each archegonium is surrounded by an individual collar of cells called 

 the perianth. 



The stalk of the archegoniophore is provided with the same two longi- 

 tudinal grooves that we have noted were present in the antheridiophore, and 

 it has been suggested that the function of these grooves is to provide a water 

 channel in which the antherozoids may swim down the antheridiophore and 

 up the archegoniophore to reach the archegonia. We do not really know 

 precisely how the male gametes find their way to the archegonia, but from 

 the fact that fertilization of the oosphere is effected we know that they 

 must do so. When we consider not only the distance between the sex organs 

 and the ground but also the fact that the sexes are on difi"erent plants, we 

 can clearly see the difiiculties in the way of fertilization by a microscopic 

 antherozoid, and the advantages of having a good method of vegetative 

 propagation. 



The result of fertilization is the development of a sporogonium in a 

 way similar to that in Pellia. The oospore divides into eight cells, four of 

 which form the foot and the seta, whilst the upper four cells give rise 

 to the capsule. The details of this development are sufficiently similar 

 to those in Pellia for it to be unnecessary for us to consider it in detail. It 

 is interesting to note, however, that during the development of the sporo- 

 gonium the stalk of the archegoniophore may elongate considerably, but not 

 the stalk of the sporogonium, as in Pellia, whence we are forced to conclude 

 that the reaction produced as a result of fertilization is not restricted solely to 

 the embryo, but extends also to the tissues surrounding it. As the sporogonium 

 hangs downwards the elongation of its stalk would merely carry the spore 

 capsule down to the ground (Fig. 390). 



When mature the sporogonium becomes yellow in colour and splits open 



