58 OUTLINES OF PLANT LIFE. 



EXERCISE XV. 



Marsh Marigold (Callha paluslris). 



1. Examine the roots. Observe {a) tlieir surface, wrinkled from sliort- 

 ening; (b) their structure. 



2. Cut a transverse section as in fern; observe that mechanical tissues 

 are vi'anting. 



3. Bisect longitudinally the base of a plant. Observe, as shown by 

 the origin of leaves, the variable length of internodes; at base the inter- 

 nodes are very short so that leaves are crowded ; in the middle the inter- 

 nodes are long and leaves distant; above, the internodes become shorter 

 until, in the flower, they are not developed and the leaves are very much 

 crowded. (T[ 104.) 



Study one of the well developed foliage leaves (T]" 123). Observe 



4. The broad rounded blade with slight branches (teeth) at the margin. 



5. The long slender stalk, petiole, gradually passing into 



6. The sheathing base, in upper leaves branched to form two stipules. 



(IT I25-) 



7. Examine and compare the various forms of leaves : (a) the lowest, 

 having sheathing bases without petiole or blade, passing gradually into 

 [b) the best developed foliage leaves; (c) these near the flowers losing pet- 

 iole and diminishing blade, becoming bracts; {d) the yellow perianth 

 leaves; [e) next within these the yellowish stamens; {/) the flattened pod- 

 like green carpels each forming a simple pistil. (^^ 133, 134.) 



(Further study of flcwer, p. 210.) 



68. Summary. — In fernworts and seed-plants the sexual 

 generation is small, often microscopic, while the non-sexual 

 generation is conspicuous and often long-lived. The nutri- 

 tive work of the gametophyte is either temporary, ceasing 

 when the sporophyte develops green leaves, or is entirely 

 wanting. The sporophyte forms stems, leaves, and roots and 

 does most of the nutritive work. These members are very 

 various in form and are described in the following chapters. 



