138 



BOTANY. 



in some cases provided with sucker-like organs, by means of 

 which they come into a more intimate relation to their hosts. 



176. Particular Relations of Phyllome to Caulome. 

 Sachs* has formulated the relations of phyllome to caulome 

 in substance as follows : 



(1.) Phyllomes always originate from the Primary Meris- 

 tem of the punctum vegetationis ; fully differentiated tissues 

 are incapable of producing them. 



(2.) They are always exogenous formations ; that is, they 



FIG. 119. 



FIG. 118. 



Fig. 118. Diagrams of dichotomous branching. A, normal dichotomy, in which 

 each branch is again dichotomously branched ; S, helicoid dichotomy, in which the 

 right-hand branch, r, does not develop further, while the left-hand one, I, is in every 

 case again branched ; C, scorpioid dichotomy, in which the branches are alternately 

 further developed. After Sachs. 



Fig. 119. Diagram of botryose monopodial branching. The numerals indicate the 

 "generations." 



develop from outer and not inner tissues, consequently their 

 tissues are externally continuous with those of the caulome. 

 (3.) They always originate below the growing apex of the 

 caulome as lateral outgrowths ; they may appear singly, so 

 that no two are situated at the same height on the stem, or 

 two or more may grow at once, generally at equal distances 

 from one another in the circumference of the caulome. 



* "Text-Book," p. 131. 



