366 XXVI. KEPRODUCTION OF THE PTEBIDOPHYTA. 



we open these larger sporangia with the needles, four large spores 

 will come into view, which completely filled the sporangium, 

 and made its wall bulge locally ; if we open one of the small 

 sporangia, it proves to be filled with numerous small spores. 

 The large sporangia are female sporangia (macrosporangia), the 

 large spores female spores (macrospores) ; the small sporangia 

 and spores are male, and are distinguished respectively as micro- 

 sporangia and microspores, The small spores are triangularly 

 pointed on one side, with reticulate markings, and usually hold 

 together in tetrads. The same relations, more evident in accord- 

 ance with size, are met with on the four macrospores. We see 

 clearly upon them the triangular tapering of one side ; in order, on 

 the other hand, to be able to distinguish well the reticulately-con- 

 nected ridges on the cell-wall, it is desirable to crush the spores. 

 The walls of the microspores soon become dark brown, while the 

 macrospores remain far paler. If we examine the leaves, from 

 which we have removed the sporangia, we see the ligule arise 

 close under the place of insertion of the removed sporangium, 

 as a tongue-shaped membrane. A further removal of leaves from 

 the spike shows us that the macrosporangia are far scarcer upon 

 it than the microsporangia, but preponderate on the lower parts 

 of the spike. The ripe sporangia dehisce transversely into two valves. 



Between thumb and forefinger we will now prepare median 

 longitudinal sections both of the apex and of the lower part of the 

 spike, holding the material in such way that the section passes 

 through the middle line of a pair of leaves. In favourable sections, 

 taken from spikes still growing, we have now before us the entire 

 developmental history of the sporangia, from their rudiments to 

 the ripe condition. The apex includes the growing point with 

 the youngest leaf and sporangial rudiments. At the growing 

 point we may indeed be able to see the two- or three-sided taper- 

 ing apical cell. We see the sporangial protuberances originate 

 over the youngest leaf rudiments. We note the early origin of 

 the ligule close below the sporangial protuberance at the base 

 of the leaf. Also we may see various stages in the development 

 of the macro- or microspores from a central cell in the sporangium, 

 and of the sporangial wall. 



In conclusion, it may be mentioned that the Selaginelleae, in 

 drying, preserve so excellently, that we can use softened herbarium 

 specimens in order to study the growing point and the origin of the 

 sporangia. Sections through fresh material, as well as material 

 thus softened, can be made very transparent with potash solution. 



