\ g4 Instrumente. — Botanische Ausstellungen u. Congresse. 



special ly effective, the writer would suggest a similar function for 

 the thick, highly cuticularized epideriiiis that Covers so many 

 desertic plants, or plants that grow in places exposed to intense 

 sunlight. One can easily prove by experiment that on a hot day 

 a thin sheet of white paper considerably reduces the light inten- 

 sity. A piece of Opuntia epidermis simüarly obstructs the light 

 rays, and even though the heat rays pass, we have seen that up 

 to 40—43 C no injurious efFect follows to many plants. It might 

 further be pointed out, as Wiesner has already done, that the hair 

 covering on the leaves of certain plants will contribute to the 

 same end. 



A very remarkable movement, however, has been studied by 

 the writer during the past two summers, which need only be shortly 

 referred to here. During the Avarmer days of July and August, 

 when the shade temperature rises to 35—38° C, leaves of some 

 sensitive plants that are fully exposed, and which under a greatly 

 less intense illumination have already exhibited paraheliotropic 

 movement, begin to incurve their leaflets so as at once to expose 

 their under surface and shade the actively assimilating upper sur- 

 face. At first this was supposed to be a sign of drooping, but 

 more careful study proved it to be a normal movement, and one 

 also that is shown by many plants that are not sensitive. Among 

 sensitive plants Desmodium canadense, and among non-sensitive ones 

 Arisaema Dracunculus, Zinnia hybrida and Ambrosia trifida may 

 be mentiomd. The couditions that bring about this remarkable 

 movement need not be discussed now, but we regard it as another 

 means of protection from the intense blue violet-rays. 



Philadelphia, 2nd November 1894. 



Instrumente, Präparations- und Conservations- 



Methoden etc. 



Beal, W. J., Ruled slides again. (The Botanical Gazette. Vol. XIX. 1894. 



_p. 507.) 

 Girod, Paul ; Manipulatious de botanique. Guide pour les travaux d'histologie 



veg^tale et l'etude des familles vegetales. 2. edition, revue et augmentee. 8*. 



X, 104 pp. et 35 pl. Paris (libr. J. B. Bailiiere et fils) 1895. 



Botanische Ausstellungen und Congresse. 



Sanarelli, 0., Mittheilungen aus dem XL internationalen 

 medicinischen Congresse in Rom. (Centralblatt für 

 Bakteriologie und Parasitenkunde. Bd. XV. No. 17. p. 648 — 656. 

 No. 19/20. p. 742—745. No. 21. p. 815—822. No. 22. p. 857 

 —864. No. 23. p. 897—904. No. 24. p. 950-954. Bd. XVI. 

 No. 3. p. 114—119. No. 7. p. 297 -301. No. 8/9. p. 355—363. 

 No. 10/11. p. 456-461. No. 14. p. 574—578. No. 17. p. 695 

 —700.) 



