THE AMERICAN BOTANIST. 
seeds scattering, because thev are ripe, not on account of 
the drought. 
While both these plants are humble and valueless, each 
in its own country, three thousand miles apart, occupies 
an important position in classification, for without them 
we would have only tubular and strap-shaped florets in 
the great order of Compositte. I do not forget that some 
thistles have the limb of their florets so divided that the 
two lobes on one side are a trifle separated from the three 
on the other, but in Perezia the outer lip is only notched 
to three tiny points and the inner lip has two long lobes 
separated well down to the top of the tube. If there are 
any other members of the Composites with two-lipped 
florets in North America I would like to be informed of 
Pasadena, Cal. 
SELF-PROTECTION IN PLANTS. 
Why are some plants armed with formidable spines? 
To the average person there would seem to be no particu- 
lar reason for these objectionable adjuncts to plants. A 
true thorn is described as "a sharp-pointed woody struc- 
ture which either terminates the twig, or is itself a short 
twig or dwarfshoot." This, however, merely explains 
the morphological aspect of spines and thorns. What we 
are concerned with is the part that spines pla3' in the 
economy of plant-life. According to Luther Burbank the 
"Wizard of Horticulture," "Nature has wasted much 
energy on the spines of the cactus. I have," he goes on to 
say in an article in the Centurr Magazine, "simply helped 
her by taking away from her the necessity of producing 
them, and have ielt her free to put all her energy upon 
producing food. The cactus is now a definite food ; it can 
be eaten raw or cooked ; or preserved as ginger or melon 
rind, while the seed is the delicacy of the future. There is 
no reversion of the type, no degeneracy, no return to the 
coat of mail, but persistence in its new life and structure." 
These remarks refer to the production by him of a thorn- 
