May 2, 1898.] 



KNOWLEDGE. 



117 



pointed at the ends, and possess a single or double spiral 

 thickening-band. Their elasticity and response to chang- 

 ing conditions of moisture and dryness assist very much in 

 the dispersal of the ripe spores. 



Both spores and elaters are formed while the capsule is 

 still surrounded by its " perianth," and the upgrowth of 

 the seta commences later and takes place with great 

 rapidity. Finally, when atmospheric conditions are suit- 

 able the capsule bursts, and in the -Tundermanniacea 

 alwaj's divides into four valves. Spores and elaters are 



wall, when there are two coats, breaks through the outer, 

 and the contained protoplasm grows out into a cell-plate or 

 a cell-thread {protonona), which then buds out into a new 

 plant and develops its own arnhegonia. 



This protonema stage seems to be a " reminiscence " 

 of the algal ancestor, but it is curious that it is far less 

 evident here than in the true mosses, as will be seen later. 



Meanwhile the parent egg-bearing plant or oophyte may 

 still continue to exist, and throw out fresh shoots to bear a 

 new generation of archegonia and antheridia. 



A. — The end portion of a shoot of Sardia crenulata, a simple type of the leafy Hepaties. The terminal leaves differ 

 from the rest, and form a Perianth, at the base of whieh the reproductive organs are developed. B. — Archegonia of one of the 

 leafy Hepaties (Caloiri/um). c. — Antheridia of the same. D. — ilicrascopie section through the apex of a shoot of a similar 

 type (Junfjermannia). Two unfertilized Archegonia are shown ; one on each side. In the centre is the young " Sporophyte" 

 resulting from the fertilizat on of a third Archegonium. The archegonial wall stUl remains as the Calyptra. with the lower part 

 of the neck, but has enlarged with the growth of the Oospore. The latter is already undergoing internal division to form Spores 

 and Elaters. E. — The apical portion of a shoot of Nardia, showing an Antheridium and two imfertiiized Archegonia. In the 

 centre is the Sporophi/te, consisting of a globidar Sporangium carried up on a Stalk or Seta, and sheathed at the base by the 

 remains of the Archegonium. F. — A ripe Sporangium or Capsule of Radula complanata at the moment of dehiscence, showing 

 the splitting of the wall into four valves, and the ejection of the numerous Spores mixed witli Elaters. G. — Spores and Klaters 

 magnified. (A and E, after Engler; D, after Hofmeister; B and c, after Gobel.) 



thrown out and dispersed together. In some genera a 

 number of elaters remain attached at one end to the tips 

 of the segments of the capsule, but in the genus which 

 forms the subject of our illustration they are all free. It 

 is very interesting to note that, while the mosses and ferns 

 dispense with this assistance to the liberation of the spores, 

 it should occur in such different groups as the liverworts 

 and the horsetails. Further, that a similar phenomenon 

 is seen in those strange fungi, the ilyxomycetes ; and that 

 a somewhat similar mechanism is employed in dispersmg 

 the seeds of some flowering plants. 



The spores themselves are small spherical bodies with a 

 single or double wall. Under suitable conditions the inner 



If, then, we summarize the results of our study of the 

 liverwort, regarding especially the mode of reproduction 

 and the interrelationship of the two stages of its Ufe, we 

 arrive at some such conclusion as this : — 



When the water alga? tried to Uve on land some of them 

 were able to do so with little change of structure and still 

 retain their primitive character. Others gradually advanced 

 by a specialization of the reproductive process and the 

 evolution of archegonia, whether or not accompanied by 

 increasing complexity of the thallus. This advantage in 

 the life struggle was followed up by the persistence of the 

 connection between the fertilized egg-cell, with its resulting 

 growths, and the parent plant ; just as the evolution of 



