176 



BOTANY. 



which extend lengthwise and which alternate with furrows. 



Further, the ridges of one node alternate with those of the 

 internode both above and below. Likewise the leaves 

 of one node alternate with those of the nodes both 

 above and below. 



289. Sporangia. — The end of this fertile shoot we 

 see possesses a cylindrical to conic enlargement. This 

 is the fertile spike, and we note that its surface is 

 marked off into regular areas if the spores have not 

 yet been disseminated. If we dissect off a few oi 

 these portions of the fertile spike, and examine one 

 of them with a low magnifying power, it will appear 

 like the fig. 151. We see here that the angular area 

 is a disk-shaped body, with a stalk attached to its 

 inner surface, and with several long sacs projecting 

 from its inner face parallel with the stalk and surround- 

 ing the same. These elongated sacs are 

 the sporangia, and the disk which bears 

 them, together with the stalk which at- 

 taches it to the stem axis, is the sporo- 

 phyll, and thus belongs to the leaf series. 

 These sporophylls are borne in close 

 whorls on the axis. 



290. Spores. — When the spores are 

 ripe the tissue of the sporangium be- 

 comes dry, and it cracks open and the 

 spores fall out. In fig. 152 we see that 



Portkm'of t ' ie s P ore ^ s covered with a very singular coil which 

 fertile plant \[ es close to the wall. When the spore dries this un- 



o f Eqmse- r 



tum arvense, co ii s an d thus rolls the spore about. Merely breathing 

 leads' ls and upon these spores is sufficient to make them perform 

 s h fke fru ' tinB ver y cur ' ous evolutions by the twisting of these four 

 coils which are attached to one place of the wall. 

 They are formed by the splitting up of an outer wall of the 

 spore. 



Fig. 151- 

 Peltate sporo- 

 phyll of equise- 

 tum (side view) 

 showing sporan- 

 gia on underside. 



