136 The Ottawa Naturalist. [Jan. 



9.3C. (15. 3 F.); of the Saxifrage, 14. 2 C. (6.4F.); and 

 of the black Hellebore, 15.8C. (3.6F.); that is, when the 

 temperature in the inner part of the above plants has fallen to 

 the respective temperatures. Only a few of the examined seed- 

 plants show a lower temperature ; e.g. the pontine Rhododendron, 

 23 C. (9.4F.); Ivy, 23. 3 C. (9.9F.); Holly {Ilex aqui- 

 folium), 24C. (11. 2 F.); and the Yew, 24. 9 C. (12. 8 F.). 

 The mosses are killed between 14 and 19 C. (6. 80 to 2. 2 F.) ; 

 the lower vasculiferous plants, which live in water, are not killed 

 above 15. 5 C. (4.l F.); those living on land even not above 

 31 C. (23. 8 F.); and the one bacterium experimented upon by 

 Rein required 47 C. (52. 6 F.) for killing it. 



The above temperatures are somewhat affected by the 

 temperature to which the plants have been subjected for some 

 time beforehand. For instance, potatoes that have been at a 

 temperature for some time between to 1 C. (32 to 30. 2 F.) 

 are frost-killed at 3. 08 C. (26. 4 F.), whereas potatoes that 

 had been kept for four to seven weeks at 22. 5 C. (72. 5 F.) 

 were killed at 2.14C. (28. 1 F.), that is at .94 C. (1.7 F.) 

 higher temperature. And this is the case too with other vege- 

 table products. 



CORRESPONDENCE. 



The Editor, Ottawa Naturalist: 



Mr. Macnamara's interesting article on "Poison Ivy" in 

 the May Number has only just come under my notice. Poison 

 Ivy (Rhus Toxicodendron) is common in our local bush. 

 To educate people in its characteristics I sometimes pick it 

 and have it in the house for a few days. Cases of dermatitis 

 ascribed to Poison Ivy are fairly common every summer. 

 Surely an important point is missed in all discussions on this 

 subject by neglecting the main underlying cause of this, as of 

 so many other skin inflammations. This cause is the blood 

 condition induced by auto-intoxication, a term now well under- 

 stood by the medical profession. This is not the place to go 

 further into details, but I may say that in my eleven years of 

 western experience I find the best treatment is the preventive 

 measure which cleanses the intestinal canal thoroughly and 

 which instructs the susceptible individual in a right dietary. 

 My belief is that very few people are susceptible to Poison Ivy 

 if they protect themselves in this way. 

 ^><Z\KV H. M. Speechly, Pilot Mound, Man. 



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