734 



LECTURE XLI. 



each of which is provided with two cilia : these are the antherozoids, D in Fig. 415, 

 About the time when the neck of the oogonium opens, the antheridium also bursts at 

 the apex, and allows its numerous antherozoids to escape. For reasons which will 

 appear later it is not very probable that the fertiUsation which now follows takes place 

 between the two sexual organs which, as in the figure, stand close together ; on the 

 contrary, it is probable that as a rule the antherozoids of another sexual apparatus 

 effect the fertilisation of the posphere in the oogonium. At least one antherozoid 

 enters the oosphere, whereupon the latter becomes clothed by a thick firm membrane, 

 and, after the whole oogonium has become separated from the parent plant, the 

 dormant period sets in, after which the fertilised and encysted oospore is in a con- 

 dition to germinate. 



With the reproductive processes last described, although they take place in an 

 Alga so simple as to be even non-cellular, we have, as already stated, nig^dean 

 a pproa ch to the typical repro ductive processes of the Mosses and higher Cryptogam s. 

 In fact the allernation ot generations (the first as yet dim beginnings of which, more- 

 over, are to be recognised in many other Algse and Fungi) here comes more clearly 

 into view. 



We may now turn to the reproduction of the Moss^ and since it is by no means 

 my object to give a complete review of all the subdivisions of the Vegetable King- 

 dom, I shall take from the whole of this immense group (passing over the Liverworts) 

 only one example from the subdivision of the true Mosses, selecting the most highly- 

 developed forms. 



Fig. 416 may serve for preliminary guidance in the matter.. It represents one 

 of our commonest Mosses, Catharinea undulata, at the height of its development. 

 There are to be noticed numerous erect shoots furnished with leaves, and bearing at 

 their apices the ' Moss-fruits ' or Sporogonia ; these are curved capsules on long 

 slender stalks, each being provided with an anterior beak, and clothed with a cap, the 

 so-called icalyptra . These apparent ' fruits,' however, are something quite different 

 from the fruits of a Flowering-plant. If it is wished to obtain the latter — e. g. the 

 cherries from a Cherry-tree — separately and independent, they must be torn or cut away, 

 for such fruits are part of the plant on which they are situated. The case is quite 

 otherwise with the Moss, however. With a little force, the stalk of the ' Moss-fruit ' 

 can be easily pulled out from the shoot in which it is situated ; its tissue is not really 

 continuous wi th that of the shoot, but the stal k is sim ply stuc k^Qjo speak, mtoT 

 sheath. The developmental history shows that the so-called Moss-fruit is, as a matter 

 of fact, not a part of the parent plant at all, but an independent body of quite different 

 organisation, which is situated on the green leafy shoot of the Moss-plant like a 

 parasite, and simply for purposes of nutrition. We see in the figure, in fact, the two 

 chief phases of the life-history— the two alternate generations. The Moss-plant, con- 

 sisting of roots and leafy shoots, was developed originally from a spore, and was thus 

 produced g^exually ; on the leafy shoot were subsequently developed the two kinds of 

 sexual orgajis,' female (archegonia) and male (antheridia). Each archegonium con- 

 tained an oosphere, and each oosphere, after fertilisation, by means of very slow growth 

 and numerous cell-divisions, developed into a Moss-fruit, and this in its turn finally 

 brings forth asexually developed spores in the capsule ; the capsule opens by the anterior 

 beaked portion falling off like a lid, and the spores fly out like dust. The Moss-plant^ 



