292 PRACTICAL BOTANY 



Thus (1) in the HymenophyllacecK^ &c., there is a single central 

 bundle, an arrangement which is found also in the young seed- 

 lings of other more complex forms ; (2) in species of Davallia 

 and others with horizontal stems the ring consists of two stronger 

 bundles, one running parallel to the upper, the other to the lower 

 surface ; between these are on each side several smaller bundles 

 which, together with the two stronger ones, form an interrupted 

 ring as seen in transverse section ; (3) in other cases there are 

 several (in Pteris two) concentric rings of bundles, which give off 

 branches to the leaves, &c ; (4) again, in the stems of Tree-Ferns a 

 cylindrical network is present, somewhat like that of Aspidium, 

 but with additional bundles which ramify in the central pith, and 

 also in some cases in the cortex. 



There is great variety also in the disposition of the strengthen- 

 ing tissue or sclerenchyma in different types of Ferns : thus it may 

 be absent, as in species of Davallia ; or it may be present as a thin 

 peripheral band, as in Aspidium ; or it may be present as thick 

 brown masses, as in Pteris and in Tree-Ferns. 



V. Remove from the apical bud the large quantities 

 of scaly hairs (ramenta), so as to lay bare 



1. The young leaves, with their circinate vernation. 



2. The broad apex of the stem with leaves in 

 various stages of development around it. 



3. The young roots which will be found already 

 present on the bases of very young leaves. 



4. The young buds which may be observed at a 

 very early stage on the posterior side of the leaves. 



III. Microscopic Investigation. 



VI. Cut transverse sections of the stock of Aspidium : 

 it is hardly to be expected that a transverse section of 

 so bulky a stem as this could be cut so uniformly thin 

 that the structure of all the tissues could be well seen ; 



