242 
F. E. Fritsch. 
very early stage, the thallus of the Hepaticse arising from the 
creeping base, that of the Musci from the upright system. The 
Moss-protonema appears as a relict of the original creeping base, 
bearing, as it does, the upright and radial Moss-plant as a lateral 
branch. There is no difficulty at all in making these assumptions 
with the facts given in the foregoing pages before us. 
The derivation of Bryophyta and Pteridophyta from one common 
ancestral algal group,although their further development is presumed 
to have proceeded on very different lines, is quite sufficient to 
explain the resemblances between sexual organs, etc. in the two 
cases. Moreover it should be noted that these resemblances are 
much more pronounced in the gametophyte (whose origin is assumed 
to be very similar in the two groups) than in the sporophyte (whose 
origin is regarded as very different in the two cases). 
Looked at from the point of view of a group betraying charac¬ 
teristics indicative of the probable origin of the higher plants, it is 
significant that the Chaetophorales exhibit more potentialities than 
any other group of the Isokontae. A brief summary will suffice to 
illustrate this point:— 
1. Great range of morphological construction. 
2. The most highly differentiated sexual organs encountered 
among the Isokontae (in Coleochcete). 
3. The most marked development of the zygote as an indepen¬ 
dent generation (in Coleochcete). 
4. Although the bulk of the present-day forms are found in 
freshwater (a fact which is not insignificant when we consider that 
the higher plants are likely to have had an origin from freshwater 
forms), a certain number are marine (e.g. Pringsheimia). 
5. One whole series, the Trentepohliacese, are terrestrial. 
6. A number of forms have become endophytic, being either 
subcuticular ( Endoderuia) or intercellular. 
7. There is further great diversity of habitat; thus, Tellamia 
penetrates into the shells of Molluscs, Gomontia into calcareous 
substrata, whilst Dermatophyton grows on the testa of freshwater 
tortoises. The species of Trentepohlia play a part in the formation 
of Lichens. 
8. Some forms (e.g. Cephaleuros, Acvochccte parasitica) are 
parasitic. 
9. A number become encrusted with carbonate of lime (e.g. 
Gongrosira). 
