M. Miiller on the Development of the Lycopodiacese. Ill 



centrated at this point. This is in fact the case. In that situ- 

 ation where the root is to be formed, the cells soon become 

 filled with a matter which distends them and is reddish like 

 the often-mentioned material for development [cytoblastemd) . 

 The root now begins to shoot outward, and may indeed be caused 

 to project out by a simple mechanical process, by the expansion 

 of its cells. The elongation continues to increase, the apex of 

 the rootlet always remains filled with cytoblastema, and the older 

 portions finally exhibit perfect cells, among which a delicate vas- 

 cular bundle then soon penetrates, being a branch from the larger 

 one of the axis of the branch (PL IV. fig. %). 



3. The leaves. As to their form and position, these conditions 

 have already been examined in the germinating plant, to which 

 1 have only to add, that the perfect leaf of the axis of the branch 

 is produced downward at its posterior face into a kind of tail, is 

 enlarged into a roundish projection, and has the base so detached 

 from the axis of the branch, that this apparent appendix looks 

 like that appendage which we at first found on the basis of the 

 envelopes of the bud (PI. III. figs. W d, Wx). However they 

 cannot be confounded, since that is always a much more delicate, 

 simple membrane, while here the green cellular tissue of the leaf 

 usually extends to the apex of the appendage. It is only neces- 

 sary, then, to speak of the relations of the leaf to the axis of the 

 branch. 



When a leaf is about to be developed upon this, a little eleva- 

 tion may be perceived upon its terminal bud. This prominence 

 consists of an evident extension of the parts at the circumference 

 of the axis of the branch, i. e. the young leaf at its first appearance 

 is a flattened shoot, which has only to become extended in 

 length and breadth to form a perfect leaf. In the interior of this 

 shoot the material for development {cytohlastema) shows itself, 

 and as the lamina extends itself, the cytoblastema is gradually 

 converted into cells. At the same time, and equally keeping pace, 

 a branch of the central vascular bundle — which always reaches 

 almost to the point of the terminal bud and also keeps pace with 

 its elongation — proceeds across through the delicate parenchyma 

 in the interior of the leaf (PI. III. fig. II), where it terminates 

 abruptly or in a clavate form, as in Ferns. At the same time, 

 the long parenchymatous cells clothing the vessel naturally ac- 

 company it into the leaf, and around these assemble also the 

 tubular cells. And thus the tissue of the leaf appears spongiform 

 in the cross-section. 



It must here be noticed, that both in the young branches and 

 in the terminal bud, the surface of the axis of the branch is 

 formed of a single layer of elongated cells (fig. 13), while at a 



