1896. NOTES AND COMMENTS. 225 



maintained the conclusion Professor Plateau deduces from the experi- 

 ments to which we refer. It is quite a comfort to find that we may- 

 still believe what we actually see, viz., that ilowers do attract insects- 

 After all, it is only " the vexillary function of Delpino " that disappears, 

 and so we may hope that naturalists will continue to exist in spite of 

 the views of the Director of Kew. The experiments of the Professor 

 at Gand are somewhat of the nature of a reprieve. 



A Poisonous Orchid. 



Cypripedium spedabile, a relative of our rarest native orchid, the 

 lady's slipper, and one of the prettiest of the family, as well as the 

 oldest in cultivation, has recently been proved remarkable for some- 

 thing besides its geographical distribution. It has long been known 

 from North America, where it grows in peat bogs and tamarack 

 swamps, from Nova Scotia to Minnesota, and in all the States east 

 of the Mississippi. Quite recently, however, it has been found in the 

 western provinces of China, thus adding another to the list of species 

 to which Asa Gray drew attention as indicating so striking a relation- 

 ship between the floras of the Atlantic States of North America and 

 Eastern Asia. In part vii. of the Minnesota Botanical Studies, issued 

 by the Geological and Natural History Survey of the State, a short 

 paper by D. T. MacDougal confirms the presence of poisonous 

 properties in the leaves and stems of adult plants of this and two 

 other Cypripediums. Experiment showed an irritant action on the 

 skin similar to that caused by handling various species of Rhus, the 

 poison ivy. The poison was found to reside in the glandular hairs, in 

 which the secretion, of an oily nature, is deposited in the same manner 

 as in the Chinese primrose, that is, between the cell-wall and the 

 cuticle of the terminal cell of the hair, and is set free by the final rupture 

 of the cuticle. It is suggested that the poisonous property is a 

 device primarily for the protection of the reproductive portion of the 

 plant, as the irritant action, and the amount of secretion, increase with 

 the development of the plant, reaching a maximum during the 

 formation of the seed-capsules. A propos of Cypripedium, the same issue 

 contains some remarks on the genus, with an illustrated monograph of 

 the species found in Minnesota, in which Natural Science is quoted 

 as the authority for certain statements which, hailing originally from 

 the Orchid Review, formed the subject of a " Note and Comment " in our 

 Journal. The Orchid Revieiv is apparently unknown so far west as 

 Minnesota. 



The Temperature of Plants. 



" Tree Temperatures " is the title of another of the Studies 

 referred to in our last Note. During the first six months of 1894, 

 R. W. Squires made an exhaustive series of observations on the 

 temperature of a trunk of the Box-elder {Acer Negundo) and the 



