DIRECTIONS FOR LABORATORY STUDY. 385 



1. The slender roots (all secondary); their places of origin. 

 (1" 76.) (Structure quite like ferns.) 



2. The stem; its nodes and internodes; longitudinal shallow 

 furrows and low ridges. 



3. At each node a toothed sheath (representing a circle of 

 leaves not distinct from each other), best seen on younger region. 



Cut a transverse section of the stem; mount; observe 



4. A circle of large air-canals, one opposite each furrow. Trace 

 these lengthwise in an internode. Do they pass the node? 



(IF 129.) 



5. Within the circle of air canals, the tissues constitute the stele. 

 Opposite each surface ridge, a cluster of small cells looking 

 denser than adjacent tissues. These are the cut ends of the 

 vascular bundles. (^[ 131.) 



(If underground stems are lacking make out this structure in 

 the aerial ones, which differ mainly in being hollow.) 



Examine one of the flesh-colored aerial shoots in water (fig. 

 235, A). Observe 



6. Similar distinction into nodes and internodes. Break the 

 stem by a lengthwise pull. Where does it break ? There is an 

 intercalary zone of growth at the base of internode. (Compare 

 leaves, *[F 169.) 



7. The large sheath at each node, the leaves. Each tooth 

 represents a scale leaf. Note relation of teeth to ridges of 

 stem and to those of sheath next above or below. (^ 160.) 



8. The different leaves near apex, separate, but whorled and 

 crowded in a cone; these are the sporophylls. (T[^[ 324, 325, fig. 

 235.) Note the lowermost whorl united and forming a sort of 

 collar.* 



Dissect off several sporophylls in a small dish of water and 

 observe 



9. Their parts, the stalk, the head; hexagonal form of head 

 due to crowding. 



10. The six to ten thin sacs under the head and parallel with 

 stalk, the sporangia. (Fig. 236.) 



11. Tear open a sporangium. Leave the spores in a pile on one 

 slide and mount a bit of the wall on another. In the latter ob- 

 serve the cells with thread-like spiral thickenings on the walls; 



* This may be considered a primitive perianth (IT 353) and gives added reason for 

 calling the whole cluster a flower. 



