THE GENERAL SHAPES OF PLANTS. 123 



made to lose tlieir homogeneity of form and distribution. 



Vegetal aggregates of the second order are usually fixed : 

 locomotion is exceptional. Fixity implies that the surface 

 of attachment is differently circumstanced from the free sur- 

 face. Hence we may expect to find, as we do find, that 

 among these rooted aggregates of the second order, as among 

 those of the first order, the primary contrast of shape is 

 between the adherent part and the loose part. Sea vfeeds 

 variously exemplify this. In some the fronds are very 

 irregular and in some tolerably regular ; in some the form is 

 pseudo-foliar and in some pseud-axial ; but differing though 

 they do in these resjDects, they agree in having the end 

 which is attached to a solid body unlike the other end. The 

 same truth is seen in such secondary aggregates as the com- 

 mon fungi, or rather in their immensely- developed organs of 

 fructification. A puff-ball, Fig. 192, presents no other 

 obvious unlikeness cf parts than that between its under and 

 upper surfaces. So too with the stalked kinds that frequent 

 our woods and pastures. In the types which Figs. 193, 

 194, 195, delineate, the unlikenesses between the rooted 

 ends and the expanded ends, as well as between the under 

 and upper surfaces of the expanded ends, are obviously 

 related to this fundamental contrast of conditions. Is"or is 

 this relation less clearly displayed in the sessile fungi which 

 grow out from the sides of trees, as shown at a, b, Fig. 

 196. That which is common to this and the preceding types, 

 is the contrast between the attached end and the free 

 end. 



From what these forms have in common, let us turn 

 to that which they have not in common, and observe the 

 causes of the want of community. A puff-ball shows us 

 in the simplest way, the likeness of parts accompanying 

 likeness of conditions, along with the unlikeness of parts 

 accompanying unlikeness of conditions. For while, if we 

 cut vertically through its centre, we find a difference be- 

 tween top and bottom, if we cut horizontally through its 



