184 



PRACTICAL BOTANY. 





FIG. 110. Prothallium of a Fern. Among the rhi- 

 zoids on the lower part of the figure are several 

 antheridia. Above them, near the sinus of the 

 heart, are archegonia. A single antheridium 

 with escaping antherozoids is seen at B ; an 

 archegonium is seen in section at A, showing 

 the egg cell and the tube leading to it. Through 

 the tube a drop of mucilage is being discharged. 

 (After Luerssen.) 



transverse sections of the stems. There 

 differences in the modes of reproduction, 



sieve tubes, are 

 found. Here, too, 

 for the first time, 

 a distinct, well- 

 differentiated epi- 

 dermis occurs, 

 with stomata, or 

 breathing pores, 

 resembling those 

 of the higher 

 plants. 



In size there is 

 also much ad- 

 vance, for some of 

 the Ferns in tropi- 

 cal climates reach 

 the size of trees. 

 In the arrange- 

 ment of the wood 

 there is, however, 

 a marked differ- 

 ence from the 

 arrangements in 

 both monocotyle- 

 donous and dico- 

 tyledonous plants 

 of the highest 

 branch. This is 

 especially notice- 

 able in the shapes 

 and positions of 

 the fibrovascular 

 bundles as seen in 

 are also marked 



