IN PTERIDOPHYTA 



2. BRYOPHYTA. 



The few examples of the Bryophyta I have referred to above must 

 suffice here for the group ; the interesting phenomena of their germination 

 will be described in full detail in the special part of this book. 



I may however point out that the juvenile form, the protonema, is not the only 

 interesting feature in their history : the similarity of the primary leaves of the young 

 moss-plant, in species exhibiting a special adaptation in their adult leaves, with the 

 simpler leaves of other mosses is another point worthy of notice. This happens in 

 Sphagnum, Fissidens, Polytrichum. 



3. PTERIDOPHYTA. 



The development of the sexual generation will be treated of in detail 

 in the special part of this book ; here I have only to consider the juvenile 

 stages of the asexual generation which are interesting in relation to the 



FIG. 92. Primary leaves of Ferns. /, // Scolopr-ndrium ofiicinarum ; j, 4 Aspleniutn Ruta-muraria ; 5 old leaf 

 of Asplenium viride. Magnified. 



question now under discussion. The aquatic Pteridophyta will be 

 mentioned along with the aquatic Angiosperms. 



Equisetineae and Lycopodineae are essentially homoblastic in their development. 



The ferns are, as is well known, distinguished by great diversity in the form 

 of their leaves; the primary leaves however are uniform even in ferns whose adult 

 leaves are very different from one another. Fig. 92 illustrates this. It gives 

 a representation of the primary leaves of Asplenium Ruta-muraria and of Scolo- 

 pendrium officinarum, two ferns whose adult leaves are as different as possible, those 



