112 M. Miiller on the Development of the Lycopodiacese. 



later period several layers of similarly elongated cells clothe it 

 (fig. lU). 



The surface of the young leaf of L. denticulatum therefore 

 consists of but one single layer of cells, which developes into 

 the proper epidermis, subsequently contains porous orifices, and 

 always remains as a membrane composed of a single layer. Its 

 cells are always hyaline and of flattened form. Next to it inte- 

 riorly follows a layer of larger, round cells, next the spongiform 

 tissue, and lastly, the vascular bundle with its appurtenances. 



The larger, round cells originally possess a nucleus which is 

 firmly attached to the interior of the cell-wall : it is green and 

 somewhat compressed. In this form it resembles a cytoblast, 

 persisting in the cell, and I consider it as one, and that it has 

 been converted into chlorophylle. Subsequently it separates into 

 several granules, but not into many (fig. 11 c). 



The leaves are consequently only prolongations of the paren- 

 chyma of the axis of the branch-axis, and never attain an inde- 

 pendent position, as they universally remain attached by the 

 whole base. 



The relations of the leaves to each other is such, that the older, 

 the inner face of which have by this time become concave, over- 

 lie the younger, and so on until we arrive at the delicate termi- 

 nal bud which is completely inclosed by them, and, like the 

 young, delicate and almost transparent leaves, is thus protected. 



4. The organs of reproduction. I now come to a point which 

 is undoubtedly the most important of all, since it exercises the 

 most direct influence over the systematic position of the Lycopo- 

 diacece. This is the morphological import of the organs of repro- 

 duction. Having been long known, this question has not passed 

 unnoticed. The first who expressed an opinion on the subject 

 was Bischofi" in his ^Lehr. d. Bot.' 1 Th. 421. He says, "The 

 position of these fruit (this refers both to the oophoridia and an- 

 theridia) in the axil of the leaf appears to indicate that they are 

 buds, the leaves of which, united in the younger stages to form 

 the envelope of the fruit, separate when it is mature ; they do 

 not possess however the epidermal layer on the upper face. In 

 favour of this view may be instanced the two- or three-chambered 

 fruit of the foreign genus Psilotum, in which, at its first appear- 

 ance, the corresponding number of leaves may be perceived, and 

 which generally resembles in structure a chambered capsular 

 fruit.^' 



On the other hand, H.Mohl in his memoir above-cited (Morph. 

 Betr. iiber das Sporang., &c.), p. 29, opposes this, and for two 

 reasons : " In the first place,^^ he says, " it appears that the spo- 

 rangium is not actually situated in the axil of the leaf. This is 



