GROWTH AND MOVEMENT 481 



succumbing in a losing fight ; but a cutting from it is now a thrifty, well- 

 grown tree on the Boston Common. 



Reproduction. — In the smaller plants the inception of unfavorable- 

 conditions is often a signal for the gathering together of all the living 

 material into a form that can endure adversity, as with the encystment 

 in bacteria, fungi, and algae. Under these circumstances also the pro- 

 toplasm is divided into several or many parts, each appropriately pro- 

 tected; thus multiplication becomes possible if more than one part es- 

 capes injury and finds suitable conditions again for development (see 

 Bolrydium, p. 33, and many other illustrations in Part I). This simple 

 situation has been worked out, in the higher plants, into elaborate mech- 

 anisms of reproduction, which are now not always obviously related to 

 the inception of unfavorable conditions. Yet methods of cultivation in- 

 dicate that the formation of spores, even in the seed plants, in which 

 naturally it often far precedes the period of flowering, may be initiated 

 by conditions unfavorable for vegetative growth. Until these conditions 

 can be more exactly designated and analyzed, it is unprofitable to con- 

 sider them more in detail. At present, then, all that can be said is that 

 unfavorable conditions bring about a redistribution of the living mate- 

 rial, of which as much as possible resists and persists. Thus, since the 

 beginning of things, we assume, there has been an unbroken chain of 

 living matter, shaping itself for a time into organisms more or less com- 

 plex, and then retiring into the simplest and least exposed forms, to begin 

 another cycle of development when the conjunction of internal and 

 external forces permitted. 



What is death? ^ — The abandonment by the living protoplasm of a 

 body previously constructed, or the destruction of the protoplasm wholly 

 or in great part, is what is usually meant by the death of a plant. Since 

 plants conspicuously lack individuality whenever they become more 

 complex than a single cell, the severance of a plant, even the highest, 

 into two or more parts may not bring death, as it does to so many of the 

 higher animals, but rather renewed vigor. Correspondingly, the death 

 of even a large part of the body does not necessarily bring death to the 

 whole, but often likewise renewed vigor to the parts that persist. 



Local and general death. — Extensive local death, as this may be called 

 for convenience, is possible in plants without the serious consequences 

 that follow in the higher animals, first because plants have so little spe- 

 cialization of organs and so many of the same kind; second, because they 

 have no circulatory system that might rapidly distribute to other parts 



C. B. at C. BOTANY — 3I 



