PERIODICITY IN VEGETATION. 127 
mountain lakes of this district; and Mr. Allman brought with 
him Gnaphalium dioicum and Lycopodium Selago. 
(Lo be continued.) 
Discovery of Nuphar pumila in Shropshire, by T. A. Cox. 
Mr. Editor,—TI see in the ‘ Phytologist’ for this month (p. 98) 
Nuphar pumila is mentioned as only occurring in Scotland. I 
enclose a specimen of a plant growing abundantly in a mere near 
here, which I named N. pumila without hesitation last year. It 
seems to me to agree exactly with all the descriptions of N. pu- 
mila with which I have compared it. If I have named it rightly, 
and it is not found anywhere else south of Scotland, it is an in- 
teresting addition to our flora here. Yours faithfully, 
Tuomas A. Cox. 
Ellesmere, September 7th, 1855. 

Of Periodicity in Vegetation; or the Periodic Changes which 
Plants undergo, their Duration or Longevity, etc. 
Like animals, all plants originate in seeds or spores, or in some 
modifications of cellular tissue which is capable of germination. 
When the seed or spore begins to expand or to develope itself, the 
life of the plant begins, and henceforth continues to exist and 
grow till it has completed the period of its existence, unless its 
duration has been shortened either by accident or design. This 
change from an undeveloped seed or spore to a living organized 
object is one of the most important vegetable periodic changes. 
The period which elapses between this commencement of the 
plant’s existence and its decay or death is called the duration of 
the plant, or the extent of its existence as a living object. With 
reference to duration, all plants are divided into annual, biennial, 
and perennial,—terms which do not in any case, it may be as- 
serted, precisely express the exact period of the plant’s life, and 
generally convey to the uninitiated an incorrect notion of this 
space. Perhaps the greater portion of our so-called annual plants 
do not exist a year, nor even half a year; few of them live more 
than a few months, and some of them only a few weeks. Our 
cereals, or our grain-bearing plants, germinate and ripen seeds in 
