THE MORPHOLOGICAL COMPOSITION OF PLANTS. 15 



simulating a perfect plant, with root, stem, bud, and fruit, 

 all produced by the branching of a single cell. And 

 among fungi, the genus JBotrytis, Fig. 6, furnishes an illus- 

 tration of allied kind. Here, though the size attained is 

 much greater than that of many organisms which are mor- 

 phologically compound, we are compelled to consider the 

 morphological composition as simple ; since the whole can no 

 more be separated into minor wholes, than can the branched 

 vascular system, of an animal. In these cases, we have con- 

 siclerable bulk attained, not by a number of aggregates of 

 the first order being united into an aggregate of the second 

 order ; but by the continuous growth of an aggregate of the 

 first order. 



§ 182. The transition to higher forms begins in a very 

 unobtrusive manner. Among these aggregates of the first 

 order, an approach towards that union by which aggregates 

 of the second order are produced, is indicated by mere juxta- 

 position. Protophytes multiply rapidly; and their rapid 

 multiplication sometimes causes crowding. When, instead 

 of floating free in the water, they form a thin film on a moist 

 surface, or are imbedded in a common matrix of mucus ; the 

 mechanical obstacles to dispersion result in a kind of feeble 

 integration, vaguely shadowing forth a combined group. 

 Somewhat more definite combination is shown us by such 

 plants as Palmetta botryoides. Here the members of a family 

 of cells, arising by the spontaneous fission of a parent-cell, 

 remain united by slender threads of that jelly-like substance 

 which envelops their surfaces. In some Diatomacece, several 

 individuals, instead of completely separating, hold together 

 by their angles ; and in other Diatomacem, as the Bacillaria, 

 a variable number of units cohere so slightly, that they are 

 continually moving in relation to one another. 



This formation of aggregates of the second order, faintly 

 indicated in feeble and variable unions like the above, may 

 be traced through phases of increasing permanence and de- 



