~'l)t PHYSIOLOGICAL BOTANY. PART II. 



Valisneria spirali* is one of the most remarkable. This 

 is an aquatic, native of the south of Europe. Its 

 flowers are dicecious. The females are attached to 

 long peduncles which at first are spirally twisted, so 

 that the buds are completely submerged. They after- 

 wards untwist until the buds reach the surface, and the 

 flowers expand. The males on the other hand have 

 very short peduncles, and their buds are in the form 

 of little bladders which easily detach themselves from 

 the peduncle and float to the surface of the water when 

 the pollen is ripe. Here they surround the female blos- 

 soms and then expand. The peduncles of the female 

 plants coil up again, the flowers are submerged and the 

 seed is then ripened below the surface of the water. 



(260.) Certainty of Reproduction, No one who 

 feels as he ought the lessons which the study of nature 

 is calculated to convey, but must be struck with admir- 

 ation at witnessing the multifarious resources, combined 

 with an extreme simplicity in the means employed, for 

 effecting that unity of purpose which is manifested in 

 the preservation of the numerous species that clothe 

 and beautify the surface of the earth. Independently 

 of that security which every species possesses in its 

 reproduction by seed against the probability of utter 

 annihilation, some are further enabled to maintain their 

 position by means of creeping stems. Many aquatics, as 

 the potamogetons, are thus extensively propagated at 

 the bottom of rivers and lakes and their perpetuity 

 secured, even though the conditions necessary to en- 

 able them to perfect their seed should never be ful- 

 filled. On the other hand the occasional produc- 

 tion of seed in such plants seems to be necessary, 

 if we remember that their native bed may possibly 

 be drained in the lapse of ages by one of those 

 events which characterise the geological history of our 

 planet ; when the only chance which would possess 

 of being preserved must consist in the probability of 

 some of those seeds which they had " cast upon the 

 waters," finding a new station equally congenial to 



