86 THE AMERICAN BOTANIST. 



which plants are placed is due to various bacteria which begin 

 to tear down the tissues of the plant. If the orchids do not 

 suffer this, it is probable there is something in their tissues that 

 prevent bacteria from developing. Further investigations are 

 desirable. The white lady's-slipper was without doubt an 

 albino pink one. Those who discover albino flowers of any 

 kind ought to remove them to their grounds for futher study. 

 —Ed.] 



The Cactus and Cold. — Because the various species of 

 cactus are most plentiful in arid deserts, it is often assumed 

 that they cannot endure the cold. Many kinds, it is true, 

 are adapted to warmer regions and are killed by freezing 

 temperature, but one species of prickly pear, at least, Opun- 

 tia Rafinesquii, grows along the Peace River, a tributary of 

 the Mackenzie in latitude 56° and is here exposed to tempera- 

 tures of more than fifty degrees below zero. 



Violet Seeds. — It takes a long time to be certain about 

 anything in botany. It used to be asserted, and is yet, in 

 some quarters, that the showy or petaliferous flowers of violets 

 always failed to produce seeds. So long as this was believed 

 it formed an excellent background for picturing the necessity 

 for cleistogamous flowers in this group. But now that it turns 

 out that nearly all the showy flowers can and do produce seeds 

 the reason for cleistogenes will have to be sought elsewhere. 

 It will probably be found in climate, as the writer of this long 

 ago suggested. Dr. Ezra Brainerd recently examined eigh- 

 teen species of "stemless" violets and found that all but two 

 produce seed freely from petaliferous flowers. Some plants 

 produced more than three hundred seeds. Dr. Brainerd says : 

 "The structure of the flower, in style, stamens and petals, 

 shows a most ingenious arrangement to prevent self-pollina- 

 tion ; and it was evident that the ovules are readily fertilized 

 by the pollen of an allied species. The co-existence of this 



