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16 



MR 



SCOTT ON THE TREE FERNS OF BRITISH SIKKIM 



Alsophila ornata and contaminans they form a dense mass extending hi 



and that 



jh up the stem), 



F 



the densely rooting species there is a greater tendency to a general decay 

 of the lower parts ; hut this is, again, only when a massive hasis of adventitious roots has 

 all hut neutralized the strain on the hase of the stem. Anyhow, I may state that in no 

 case have I seen the interior decay in uninjured specimens extending a foot ahove the 



gr oun d-le vel . 



Bamificcdion of >S'ifm5.— Ramification of the caudex of tree ferns is occasionally pro- 

 duced hy the suppression of the terminal hud, more frequently hy the development of 

 adventitious huds. Hofmeister, as I have stated in my prefatory remarks, further 

 divides the former mode into those in which the hifurcations are equally developed, and 

 those in which one of the forks forms the principal axis and gives to the other a lateral 

 position. To the former he applies the term Dichotomy ; the latter he distinguishes as 

 lateral huds. The application of the latter term in the sense mentioned is apt to mislead ; 

 and indeed the distinction appears to me superfluous. Practically these so-called lateral 

 shoots are ultimately in many cases undistinguishable from those having an adventitious 



origm. 



Hofmeister, indeed, maintains that there is a " real difference between the 

 internal structure of the forked branches of the stem, and that of the place of junction 

 of the principal stem with the buds which I have regarded as adventitious and seated 

 on the stipes. The former exhibit throughout their entire length the peculiar structure 

 of the stem, while the collar of the latter, on that part between the principal axis and 

 place of origin of the bud, exhibits the characteristic arrangement of the vascular bundles 

 of the stipes" (Hofmeister, 'Higher Cryptogams,' p. 266). Differences in the internal 

 structure of the two forms of buds are by no means and in all cases thus easily distin- 

 guished ; and certainly in the buds of tree ferns which have come under my observation I 

 have in no case found such distinctive characteristics as the above; adventitious buds, 

 though presenting a structure somewhat akin to that of the stipes in an incipient, have 

 little in common with them in the mature state. I have examined many of those buds in 

 nearly every stage of development on the Alsophila gigantea and comosa, both of which are 

 singularly prolific. In both these species the adventitious buds most frequently occur 

 on the outer base of the stipes, though they are by no means rare on the interspaces 

 between the fronds. Now these differently posed buds present differences in structure 

 the former directly communicating with the interior of the stem, through the frond- 

 meshes, while the woody laminse are interposed in the latter. These stlpal buds, being 

 thus manifestly in a very similar relation to the main axis as are the displaced lateral 

 axes of the forked end of stems, a considerable similarity in structure might be justifiably 

 assumed. This is confirmed by observation. Differences in the developmental force of 

 the axis of a fork are generally manifested in the incipient stage : growth is more or less 

 completely suppressed in the weak axis ; the latter is forced out on the side of the stem 

 and presents a contraction at the collar {vide PI. X. fig. 2) similar to that of adventitious 

 buds, from which it scarcely differs in structure. ^ 



, ^ The disguise is thus in many cases 



cry complete, so much so that a long-latent and subsequently developed main axis is 



only dostingmshable from the adventitious buds by its more complete and direct union 



with the interior woody framework; and 



even this is also much disguised when a 



