LVCOPODIACEyE. 



415 



of the tissue could be observed into a central mass and a wall consisting of three 

 layers; the cells of the former soon become isolated and rounded off, and if a micro- 

 sporangium is under observation, they all divide, after previous indication of a 

 bipartition (Fig. 309 E, e,/) into four spores arranged in a tetrahedron, which retain 

 this arrangement until they are ripe {g, h). In the macrosporangia, on the contrary, 

 one of these mother-cells grows more vigorously, divides, and produces the four 

 macrospores, while the rest of the mother-cells remain undivided ; but, at least in 

 S. in(2qualifolia, continue to exist for a considerable period by the side of the much 

 larger macrospores. These latter also retain until their dispersion their primitive 

 position at the corners of a tetrahedron which they owe to the division of the 

 mother-cell. Weakly macrospores are very commonly to be found in otherwise 

 normal spikes of sporangia. The three cell-layers of the wall of the sporangium 

 continue to exist until the spores are 

 ripe, while in the case of Ferns the inner 

 layers, as we know, are destroyed during 

 the formation of the spores. 



The youngest rudiments of sporangia 

 which I could detect in Lycopodiiim 

 Cha??icpcypan'ssus — but which I have fre- 

 quently examined — have the appearance 

 of broad protuberances of the upper side 

 of the young leaf, at first very flat, and 

 in this case it is quite clear that they do 

 not belong to the axil of the leaf nor to 

 the stem itself; the fibro-vascular bundle 

 of the leaf passes beneath them, and it 

 appears as if in this case the sporangium 

 is not produced from a single superficial 

 cell. In the youngest, and even in older 

 states, where it already projects as a flat 



segment of a sphere, the epidermis of the leaf is continuous over the sporangium, 

 constituting its parietal layer. While the sporangium becomes more and more 

 protuberant, this layer undergoes numerous divisions at right angles to the surface. 

 Even in the youngest stages there can be recognised, beneath the swelling of the 

 epidermis, a layer of cells, out of which, as the growth of the protuberance advances, 

 a spherical group of large cells is formed, which divides in all directions to form 

 the mother-cells of the spores. The processes appear to be still the same when 

 the sporangium has grown to a considerable size and is almost spherical in radial 

 section ; at that time a tangential division is seen here and there in the parietal 

 layer, which, in the mature state, clearly consists of at least two layers. Older 

 stages of development have not come under my notice; what I have here stated 

 was deduced from the observation of some longitudinal sections of very young 

 spikes preserved in glycerine. 



In Psilotum the short branches on which the apparently trilocular sporangia 

 arise appear as papillce on the vegetative cone, which, according to Juranyi, possess, 

 as well as the vegetative branches, a three-sided apical cell. A bundle from the 



Fig. 309 *. — A nearly ripe macrosporangium o( Se/a- 

 gmella iiMquali/olia ; the fourth spore which lies be- 

 hind is not indicated (Xioo). 



