ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 395 



uncBanged as long as it continues to elongate, wliatever the length, of 

 the branch ; and the structure of the median region is always the same 

 from the base to the summit. It follows that the tissues at different 

 levels from the vegetative zone indicate the different stages of 

 differentiation in the tissues of any given level of the median region 

 of a simple branch. The cone of growth of a simple underground 

 branch never has a pileorhiza ; it is of exogenous origin. 



The conclusion drawn from these observations is that the simple 

 underground branches of Psilotum are stipites with a single central 

 vascular bundle ; these stipites have no appendages or roots, and 

 perform the physiological function of roots. In certain regions the 

 plant is therefore reduced to a condition of extreme simplicity ; the 

 stipes playing the part of a root ; and the resemblance to a true root 

 is extremely close. Among the Lycopodiaceae, finally, there are some 

 species entirely destitute of root. 



Muscinese. 



Male Inflorescence of Muscinese.* — H. Leitgeb points out that 

 the order of development from the lower to the higher forms of 

 Muscineae is indicated by the position of the sexual reproductive organs 

 on the vegetative shoots. The advance may be described as an acropetal 

 movement of development ; the reproductive organs originating in 

 segments nearer and nearer to the aj)ex as we ascend in the scale. 

 The shoot loses in consequence more and more of its vegetative 

 character, and becomes differentiated as a special fertile shoot, which 

 again becomes more and more shortened. In the lowest forms of 

 Hepaticee, the Eicciese and Eiellese, the vegetative shoot assumes at 

 particular times reproductive functions without essentially altering 

 its character. A good example of a higher stage is afforded by 

 Plagiochasma, where the transformation is indicated by the reduction 

 of the assimilating tissue. In the greater number of Muscinese we 

 get the still higher stage of development, where the vegetative shoot 

 closes with a special " inflorescence " of sexual organs, while in Mar- 

 chantia and Lunularia a still more complete differentiation of the 

 fertile shoot takes place. Leitgeb then states that in the true mosses 

 also the first archegonium is derived from the apical cell, and there- 

 fore forms the direct conclusion of a vegetative shoot ; and argues 

 that in Polytrichum the male inflorescence is composed of partial 

 inflorescences, each of which corresponds to a reduced lateral branch ; 

 the leaves being simple protective organs to the antheridia. 



Antheridium of Hepaticse.t — H. Satter describes the structure 

 and development of the antheridium in Pellia, Monoclea, and Corsinia. 

 In Pellia ejpipliylla the antheridia are imbedded in the thallus, as in 

 MarchantiaccBB, but are of the true Jungermanniaceas type ; from 

 which he concludes that the depression of the antheridium has no in- 

 fluence on its structure. In Monoclea and Biella, on the other hand, 



* Flora, Ixv. (1882) pp. 467-74. 



t SB. K. K. Akad. Wiss. Wien, Ixxxvi. (1882). See Bot. Centralbl., xiii. (1883) 

 p. 227. 



