12 BULLETIX OF THE NATURAL HISTORY SOCIETY. 



zoospores) which can swim freely through the water b}"^ 

 means of cilia or flagelhe, precisely as animals of an 

 eqnivalent grade do. The Diatoms move by nse of 

 protoplasmic filaments, and some filamentous algte, the 

 Oscillariie, b}' viln-ating movements of their rod-like 

 structure. Among land plants, some of the slime-moulds, 

 or Myxomycetes, can creep over damp surfaces exactly as 

 the animal amoeba does, i. e., by continually causing its 

 very plastic substance to fiow in a constant direction. 

 ISTo liigher land plants whatever have the power of 

 independent locomotion. 



//. E.vte}isio)i Aicctij of Parts by Groicfh. 



In the higher plants, a branching root and stem 

 system prevails, each part of which grows only at or 

 near its tip. By sending out these growing parts laterally 

 and allowing them at a greater or less distance to turn 

 upward and grow into an erect plant, or to send ofi:' 

 an erect plant by branching, an efi:ective and rapid 

 though not extensive locomotion can be brought about. 

 The connecting part may subsequently die, leaving them 

 independent. There are several wa^^s in which lateral 

 growing parts may act. 



1. Horizontal underground roots and rhizomes, more or less 

 long and slender, may send up new plants (called "suckers") 

 from adventitious and axillary buds respectively. Examples of 

 the former are Blackberry, Asdepias Cornuti, etc., and of the 

 latter, Trificum repens, AchUln'a mUlefolium, and many others. 

 The same method occurs abundantly in water plants. It inci- 

 dentally brings about the formation of turf, and makes some plants 

 very dilficult to exterminate, and hence they become " weeds." 



2. Offsets and runners above ground form new plants at 

 their tips. The Houseleeks (Sedum), Lobelia cardinalis, show 

 the former, and the Strawberry, PotentUla anserina, etc., the- 

 latter method. 



