348 



SPONTANEOUS MOVEMENTS IN PLANTS. 



diurnal to the nocturnal position, and the contrary ; but the lateral 

 ones are continually rising and falling, both day and night, by a suc- 

 cession of little jerks, like the second-hand of a time-keeper ; the 

 one rising while the other falls. Exposure to cold, or cold water 

 poured upon the plant, stops the motion, which is immediately re- 

 newed by warmth. The late Br. Baldwin is said by Nuttall to 

 have witnessed the same thing in our own Desmodium cuspidatum, 

 in Georgia ; but the observation has never been confirmed. In 

 several tropical Orchideous plants, and especially in a species of 

 Megaelinium, the lower petal, or labellum, executes similar spontane- 

 ous movements, with great freedom and pertinacity. Such phenom- 

 ena, occurring as they do in Phaenogamous plants of ordinary struc- 

 ture may serve to render more credible the true vegetable character 

 of the 



678. Free Movements of the 



Spores of Algae, and the cor- 

 puscles or spiral filaments of 

 the antheridia of most Cryp- 

 togamous plants, already re- 

 ferred to (659 - 663). The 

 spores of most of the lower 

 Algoe are now known to ex- 

 hibit this peculiar activity 

 at the time of their dischai'ge 

 from the parent cell, when, 

 for some moments, or usual- W~-40 

 ly for several hours, they 

 behave like infusory ani- 

 mals, executing spontaneous 

 movements in the water, 

 until they are about to ger- 

 minate. This singular move- 

 ment was first detected many 

 years ago_ in Vaucheria 



FIG. 636. Fruiting end of a plant of Vaucheria geminata (after Thuret) ; one of the 

 branches still containing its spore. 637. Moving spore just escaped from the apex of the 

 other branch ; the ciliary apparatus seen over the whole surface. 638. Spore in germination. 



FIG. 639-642. Successive steps in the germination of aCdogonium (Conferva) vesicata. 

 643. The plant developed into a series of cells, four of which display the successive steps in the 

 formation of a spore. 644. The locomotive spore with its vibratile cilia (copied from Thuret). 

 When the movement ceases, and it begins to germinate, it appears as in 639. (The antheridiq 

 or fertilising apparatus of these plants were not known when these figui*es were made.) 



