TttE AMERICAN BOTANIST. Si 



iumlg-atecl in an air-tight tin box and as an additional 

 safeguard flakes of naphthalin are scattered on the her- 

 barium shelves to prevent the entrance of more insects. In 

 this way they have practically gotten rid of the pests. 

 Since the fumigation method has been found effective, 

 -efforts have been made toward securing cases that are 

 practically air-tight so that the plants can be fumigated 

 without removing them from their cases. This has result- 

 •ed in the installation at the Gray Herbarium of a series of 

 cases made of sheet steel.. An extended account of the ex- 

 periments with cases and poisons is given in Rhodora for 

 'October, 



Orchids and Symbiosis.— The comparative rarity of 

 many orchids has been accounted for upon the supposition 

 that the flowers are so dependent upon certain insects for 

 pollination that they seldom set seed, but all who have 

 •examined orchid seed-pods know that when the plants do 

 produce seed the seeds are minute and very numerous, and 

 they may have wondered how plants which can produce 

 so many seeds should still be so few in numbers. It now 

 transpires that young orchids are most successfully reared 

 if the seeds are sown in soil in which the same or similar 

 species are growing and the reason that the new plants 

 are thus able to thrive is because they form partnerships 

 wnth certain microbes common on the roots of the older 

 plants. Growers have often induced large numbers of 

 seeds to germinate, only to see them fail later for no ap- 

 parent cause. Their lack of the microbes now seems to be 

 a solution of the mysteiy. Possibly the same state of 

 affairs exists in nature, in which case the rarity of orchids 

 is easily accounted for. 



