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 of 

 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 



th e spore is covered with a very singular coil which 

 W T hen the spore dries this un- 

 Merely breathing 



151. 



Peltate sporo- 

 phyll of equise- 

 tum (side view) 

 showing sporan- 

 gia on under side. 



15- 



Portion of 



fertile plant ji es close to the wall. 



o f Equise- 



tum arvense, coils and thus rolls the spore about. 



whorls of upon these spores is sufficient to make them perform 



leaves and 



the fruiting ver y curious evolutions bv the twisting: of these four 



spike. 



coils which are attached to one place of the wall. 

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

 spore. 



