THE AMERICAN BOTANIST. 19 



No Hornbeam Trees. — Those who speak of hornbeam 

 trees are guilty of tautology for the word beam itself means 

 tree. We see the same idea in the word, boom, applied to 

 parts of a ship, and in the beams of our houses. Even sun- 

 beams are said to be derived from this source. 



Perennials Defined. — There is no doubt about a tree 

 being a perennial. Year after year the same trunk puts forth 

 new leaves, adds new twigs and for many years increases in 

 height and girth. With the so-called herbaceous perennials, 

 however, whose parts that carry them over the season, are 

 under ground the case is quite different. Many of them are 

 true perennials, and put new stems each year from identically 

 the same underground parts, but there are many other plants 

 called perennials, that produce new parts each year from which 

 the plants arise. Most of our lilies are of this kind and so are 

 the adder's-tongues. A single bulb of the common yellow 

 adder's-tongue {Erythroiiiuni Americanum) may, at the end 

 of the season, be two or three bulbs, none occupying the place 

 of the original bulb. Such plants might almost as correctly 

 be termed peculiar forms of annuals. 



Our Unstable Flora. — In botanical works we often read 

 of the "struggle for existence" among the plants, but a casual 

 walk in the fields seldom reveals evidences of the struggle. 

 This struggle is always going on, how^ever, the big plants 

 trying to choke out the little ones, the dry ground plants 

 crowding the marsh plants and these latter in their turn usurp- 

 ing the habitats of the true water species. But when any of 

 these become supreme in a locality, winners of the fight, as 

 it were, they are victors only for a time. Rainfall, wind, 

 sun, cold and many other agencies are constantly though slow- 

 ly changing the very land itself and what is now the ideal 

 habitat of a plant may in a few centuries hence be quite un- 



