212 THIRD GROUP.— VASCULAR CRYPTOGAMS. 



in Blechnum hastatum a lateral bud is formed beneath every leaf ajid becomes w 

 stolon') ; in Tree-ferns the terminal branching of the stem is reduced to a minimum, 

 either not occurring at all or only in abnormal cases. 



The formation of adventitious buds which do not originate in the terminal 

 branching of the stem is connected in the Ferns with the leaves, and in many cases, 

 in Ceratopteris, for instance, there is no terminal branching at all, and buds are formed, 

 only on the leaves. These buds appear on the stalk or on the lamina of the leaf. 

 Such shoots in Ptcris aqiiilina (Fig. 160 K) are on the back of the leaf-stalk and near 

 its base ; in Aspidiu?ti Filix-inas (Fig. 158) they appear someway above the insertion 

 of the leaf, usually on one of the lateral edges of the leaf-stalk ; in both cases they are 

 formed according to Hofmeister on the young stalk before the development of the 

 lamina and before the differentiation of its tissue ; a single superficial cell of the stalk 

 is the mother-cell of the new shoot ; as the surrounding tissue grows up round it like 

 a wall, the bud may as in Pteris be sunk in a deep depression and there remain 

 dormant for some time ; in that case the leaf-stalk continues succulent and filled with 



Fig. 159. .Isplenium decussatitm. Middle portit 

 a leaf; the midrib st bears the leaflets /, at the base of v 

 the bud k has formed and has already put out a root. 



Fig. 160. Ptcris aqiiilina. A the extremity of a stein j/. the 

 ape.\ of which is at ss ; near it at * a rudiment of a leaf, I's the 

 stalk of a leaf in its second year, at h its lamina concealed by hairs, 

 k a bud at the back of the leaf-stalk, 7v roots. JJ young leaf in its 

 second year; /ts its stalk, / its small lamina freed from hairs. 

 C longitudinal section of a similar leaf with the transverse section 

 of the stem si attached ; 6s and / as in £. D the lamina of a leaf in 

 its second year seen from the front, i.e. on the upper side. E the 

 horizontal longitudinal section of a bifurcation of the stem ; ss s's 

 the two apices, aa brown epidermal tissue, bh brown sclerenchyma. 

 .;.■ vascular bundles. A, S, C natural size, D magn. about 5 times. 



nutrient substances for some way above the bud long after the leaf has died away, 

 and in Aspidium Fih'x-mas strong stems with numerous leaves are not unfrequently 

 found connected at their lower end with a leaf- stalk from an older stem. In many 

 cases, as in Strnthiopteris germanica, these buds from the leaf-stalk develope into long 

 underground stolons furnished with scale-like leaves, which turn upwards in their 

 growth at their free extremity and unfold a circle of foliage-leaves above the ground ; 

 in Nephrolepis undulata they swell into a tuber at their extremity. Adventitious buds 

 are formed on the lamina of the leaf, especially in many of the Asplenieae '^ ; in 



Mettenius, Ueber Seitenknospen bei Farnen (Abh. d. Kon. Sachs. Ges. d. Wiss. i860). 

 On the formation of these buds see Heinricher in Sitz.-Ber. d. Akad. d. Wiss. in Wien, 



