IV] 



BUDS AND BRANCHING 



69 



the formation of a solitary leaf, and this may be held to suggest that there, 

 as in other Ferns, the alternate arrangement is fundamental. That disposi- 

 tion is maintained throughout life by creeping Ferns, and by most upright 

 Ferns as well. Where an apparently whorled arrangement of the leaves 

 supervenes, it may be held to be in the race, as it certainly is in the indi- 

 vidual, derivative from an alternate origin. 



Buds and Branching 



The shoot may remain simple, and unbranched, as it commonly is in the 

 Marattiaceae, and many Tree Ferns. On the other hand it may branch with 

 greater or less profusion. But the branches are disposed in such different 

 ways in various cases that it appears difficult at 

 first to recognise in them any common, scheme. 

 They fall, however, for the most part into certain 

 types of branching, which will first be described 

 and illustrated by definite examples : 



(I) Many Ferns show dichotomy of the apex 

 of the shoot, often with very exact equivalence of 

 development of the two limbs or shanks of the 

 forking. This may be found occasionally in up- 

 right stems with crowded leaves, as in Osvmnda, 

 Plagiogyria, and Cyathea (Frontispiece). But it is 

 in creeping axes, where the leaves are far apart, 

 that bifurcation is most common, and is most 

 readily seen. The branching may occur at some 

 distance from any leaf-insertion (Fig. 61), though 

 frequently a leaf may appear to be related to the 

 forking (Fig. 62). Such forkings are frequently 

 present in rhizomes of Lygodium, Sckizaea, Gleichenia, Lindsaya, Pellaea, 



Fig. 61. Glcichenia {Dicrano- 

 pteris) fulva, Underw., show- 

 ing dichotomy of the rhizome. 



(Nat.? size.) 



Fig. 62. Rhizome of Dryopteris Litmaeana, C Chr. ( = Polypodium 

 Dryopteris, L.) dichotomously branched, with ahernating leaves. 

 The roots are omitted. (After Velenovsky.) Reduced. 



