M. MuUer on the Development of the Lycopodiacese. 1 15 



of their occurrence varies in three ways. Either only antheridia 

 appear on the spikelets {L. Selago^ clavatuniy annotinum, inunda- 

 tum, the genus Phylloglossum, kc), or only oophoridia {L. sela- 

 ginoides), or both organs together. Here belongs L. denticu- 

 latum, apparently together with the whole genus Selaginella and 

 some annual species of the genus Lycopodium, which represent, 

 as it were, the pigmies of the Lycopodiacece, e. g. L. gracillimum 

 and pygmaum. In these two the oophoridia are situated under 

 the antheridia at different points on the spike. On the other 

 hand, in L. denticulatum and other Selaginellcs in which I have 

 become acquainted with the formation of the fruit, only one 

 single oophoridium occurs on the spikelet, and that always at its 

 base. This becomes of very great importance when we seek to 

 discover the import of the oophoridium, and will be spoken of 

 hereafter. In development however it is the simplest case, and 

 therefore the most instructive. 



Examining the base of the spikelet of L. denticulatum more 

 closely, the oophoridium is found to rest upon two leaves, two 

 folia intermedia. The spikelet, which beyond this point bears 

 only antheridia, also has intermediate leaves from its very base, 

 that is, on the side opposite the oophoridium, and the whole 

 spikelet is furnished with them. 



To trace the structure of the fruit-bearing portion of the axis, 

 we must go back to the earliest condition of the terminal bud. 

 The dichotomous division is always strongly marked in this bud, 

 since the apex of the axis is always broader and more thickly 

 clothed with leaves than the inferior portion. Inquiring into 

 which portion is developed into the fruit-stalk, a very careful ex- 

 amination shows that it is always that lying to the right hand. 

 That there may be no doubt as to left and right, the plant must 

 be looked on from above. The upper side however is always that 

 on which the folia intermedia are attached. When the axis has 

 divided into two branches, that part lying to the left of the axis 

 elongates and always divides in a similar manner further on, 

 whence it generally happens, that the direction of the right-hand 

 branch of the left axis is always diverted a few degrees towards 

 the left as in all cases of bifurcation, and thus the plant is in a 

 condition to spread to such an extent that it covers large circular 

 areas. 



So much for the fruit-bearing axis. I have now to explain 

 more specially the development of the oophoridium and the an- 

 theridia, in order to make out their morphological import. 



2. The oophoridium. — a. The formation of the sporangium, I 

 do not dwell long upon the description of this, since its structure 

 is nearly or almost wholly similar in most species, and may also 

 be regarded as sufficiently understood. It is, briefly, a sporan- 



