THE PLANT-BOD T. 67 



roots, those of epiphytes, parasites, etc. (4) Tricliome, 

 which includes all outgrowths or appendages of the surface 

 of the plant, as hairs, bristles, root-hairs, etc. Caulome 

 and Phyllome together constitute the Shoot, so that in 

 common, terrestrial, higher plants the plant-body is com- 

 posed of the Shoot in the air, and the Root in the ground, 

 with Trichomes on both portions. 



118. As indicated above, in the lower plants the differ- 

 entiation into members is not as marked as in the higher, 

 and in passing downward in the vegetable kingdom groups 

 are reached in which it is inappreciable, and finally in 

 which it is entirely wanting: such an undifferentiated 

 plant-body is called a Thallome, and may properly be re- 

 garded as the original form, or prototype. 



119. Thallome. — This properly includes all cases in which 

 the plant-body is a mass of cells, with no differentiation of 

 members, but for convenience we may include also the sin- 

 gle plates, and rows of cells, and even the single cells. 

 Plants composed of rows or plates of cells frequently show 

 no indication whatever of a division into members ; but in 

 some cases there is a little differentiation, though not car- 

 ried far enough to give rise to members. 



120. In the larger seaweeds there is sometimes so much 

 of a differentiation that it becomes difficult to say why 

 certain parts ought not to be called members. Forms of 

 this kind are instructive, as showing that the passage from 

 the thallome plant-body to that in which members are 

 differentiated is by no means an abrupt or sudden one. 



121. Caulome. — By this general name we designate all 

 axial members of the plant. In the more obvious cases the 

 caulome is the axis which bears leaves (foliage), and in this 

 form it constitutes 



