THE SPERM APHYTES. 225 



mounted in distilled water; then run 10 per cent solution 

 of common salt under the cover and observe the changes. 



8. Treat a piece of the leaf with Schultze's macerating 

 mixture until it is transparent. Examine it for fibro- 

 vascular bundles, noticing particularly the fine branches 

 that serve to connect the different bundles. How are the 

 main bundles arranged with reference to one another? 

 Where with reference to the bundles are the stomata 

 situated ? 



9. Cut transverse sections of a well-developed leaf and 

 also of a very young leaf of a seedling. How do the sec- 

 tions of the fibrovascular bundles compare in the two 

 cases ? Draw a stoma as seen in cross section. 



References for Reading. Goebel's " Classification of Plants," pp. 

 346-445 ; Vines' " Text-Book of Botany," pp. 489-569 ; Scott's " Struc- 

 tuval Botany," pp. 142-197; Arthur, Barnes, and Coulter's "Plant 

 Dissection," pp. 172-221; Bessey's "Essentials of Botany," pp. 

 225-251 ; Beyer's " Elementary Biology," pp. 155-161. 



SUBCLASS II. The Dicotyledons. The characteristic 

 that has given the name to this subclass is the pair of 

 cotyledons in the embryo which develop simultaneously. 

 The leaves are usually netted- veined. The wood is ar- 

 ranged in bundles placed in a circle, or it forms a continu- 

 ous circle around the stem, though in the anomalous 

 dicotyledons it is arranged in bundles scattered irregularly 

 through the stem, at least in some portions of the plant. 

 The parts of the flowers are usually in fives or fours, 

 sometimes in threes. The flowers are sometimes incon- 

 spicuous and colorless, but are usually conspicuous and 

 with bright-colored corollas. 



This subclass includes by far the largest number of 

 ordinary plants and trees ; it exhibits the greatest variety 

 of differentiation of stem, leaf, and flower, far surpassing in 

 these particulars all the other subdivisions put together. 



CLARK'S EOT. 15 



