30 



BOTANY 



the stems of Koses and Blackberry, and the spines upon the leaves 

 of the Century-plant, are examples of such emergences (Fig. 19, D). 



FIG. 22. A, simple hair of Hollyhock (x 60). S, section of stellate hair from the 

 calyx of the Hollyhock (X 60). C, glandular hair of Paulownia imperialis (x 60). 

 D, upper part of C more highly magnified. E, peltate hair of Elssagnus argenteus 

 (X 100). 



The Reproductive Parts 



Among the lowest organisms the same cell is both vegetative and 

 reproductive, since it divides by simple fission into two equal parts 

 which become at once new individuals, or by budding, individuals 

 of unequal size are formed. Even in the highest 

 plants there is found an analogous formation of 

 new individuals by means of suckers or runners, 

 or the artificial propagation by means of cuttings. 



In all but the lowest 

 plants, however, there are 

 developed special reproduc- 

 tive cells, which may differ 

 but little from the vegeta- 

 tive cells, or may be much 

 altered. The simplest of 

 these are the resting-spores 



FIG. 23. A, tetrasporangium of Callitham- 

 nion floccosum. B, zoosporangium of Sapro- 

 legnia sp. C, a zoospore of Saprolegnia. 



of many low Algae, developed by a thickening of the wall in the 

 ordinary cells, and other slight changes which make the spore more 

 resistant than the vegetative cells, and better fitted to carry the plant 

 through unfavorable seasons. Usually the non-sexual reproductive 



