15 
account of the structure and development of Marchantia which 
shows also some remarkable resemblances to the growth of the 
fern-prothallium. So often, indeed, in comparing the liverworts 
‘with the fern-prothallium, do we meet with the same structure 
and method of growth, that such extraordinary correspondence of 
structure, without a corresponding relationship, seems impossible. 
Of the liverworts known at present, the thallose Jungerman- 
niacee and certain Anthocerotee approach most nearly in 
structure in their mature condition, to the fern-prothallium. In 
the former, according to Leitgeb* there is always a single apical 
cell so that these plants show throughout their life a condition 
which is usually but transitory in the fern-prothallium. In such 
forms as Metzgeria too, the structure of the thallus is essentially 
the same as the prothallium of the Osmundacee. 
In Metzgeria and Aneurat as well as other related genera, 
the apical-cell is of the two-sided form and the succession of 
segments same as in the fern-prothallium. In Pe//caj it corre- 
sponds closely in form to that shown in Fig. 4, 5, and probably 
represents a higher degree of development. 
In the Anthocerotez§ there seems to be at the growing points 
of the full-grown thallus a row of similar cells, much as in the 
full-grown fern-prothallium. Whether this is preceded by a 
single apical cell in the young plant is uncertain, as our knowl- 
edge of the germination of the spores is limited to that of the 
genus Anthoceros,|| and this point does not appear to have re- 
ceived the attention it deserves. 
The Marchantiacee** and Ricciacee,tt correspond closely 
in the structure and growth of the thallus, and all, so far as is 
known, have at the growing point a row of similar cells, cutting 
off two sets of segments above and below. The germination of 
the spores in the latter group is known only in Riccia glauca, 
and according to Leitgebit is entirely similar to that of the 
#1, 6: Vol ill, 26. 
+ Leitgeb, 1. c. Vol. III. p. 40. Pl. Aes 8 Be 
Leitgeb, 1. c. Vol. III. p. 7, 53. Pl. III. 
Lietgeb, 1. c. Vol. V. p. 13. pl. I. 
i. c. p. 29. ; 
Leitgeb, 1. c. Vol. Me a a. 
1. 6. Vol. TL, p. 16, 94, TX, 
1, c, p. 23. 
