352 



BOTANY: PRINCIPLES AND PROBLEMS 



stout woody stem is secondary wood, laid down by an active 

 cambium. Its water-conducting cells are all tracheids, those 

 produced in the spring being comparatively wide and thin-walled 



Fig. 221. Fig. 222. 



Fig. 221. — Cycas. Sporophyll from ovulate cone, showing several ovules 

 attached to its side. One of these has developed into a seed. {From Strasburger, 

 after Sachs). 



Fig. 222. — Cycas. Sporophyll from staminate cone, showing numerous 

 pollen sacs or microsporangia. (From Strasburger, after Richard) . 



Fig. 223. — Staminate or "male" cones of the pine. 



and those in the summer nuich narrower and thicker-walled 

 (Fig. 63). The general structure of the vascular tissues 

 approaches rather closely to that of the angiosperms, 



