MacDougal: POISONOUS influence of cypripedium. 451 



found that the secretion begins to accumulate in the distal end 

 of the cell shortly before it reaches maturity, and filters 

 through the wall forming a reservoir between the wall and the 

 outer cuticular layer. As the amount of the secretion increases, 

 since the cuticular layer is capable of only a slight distension, 

 the wall is pushed backward into the cell-cavity, finally the 

 glandular cell is in the form of a double walled cup with the 

 protoplasm occupying the space between the parallel walls, 

 and the secretion filling the bowl of the cup, and covered by 

 the arched cuticle. In the advanced stages the cuticle is easily 

 torn and it may be found ruptured with the secretion escaping 

 in the form of an an irregular mass. On account of the 

 extremely small quantity of the secretion its exact chemical 

 nature could not be ascertained. It was found to be soluble 

 in alcohol, and gave the reactions of an oily substance. This 

 is of especial interest in view of the recent researches of Pfafl 

 and Orr, which have demonstrated that the poisonous action of 

 Rhus is due to an oil, cardoL* 



It was found further that the irritant action of the plants on 

 the skin increased with the development of the plant, and 

 reached a maximum effect during the formation of the seed 

 capsules. This corresponds with the activity of the glandular 

 cells and the amount of secretion present. While this poison- 

 ous property of the plant serves as a partial protection for the 

 vegetative organs, yet it is in all probability a device primarily 

 for the security of the reproductive bodies. It is to be noted 

 in this connection that the glandular secretions do not form the 

 sole means of protection of plants of this genus. It has been 

 noted by Stahl, ^ Mobius^ and others ^ that the peripheral 

 layers over the entire body of plants of this group are fur- 

 nishe4 with a large number of cells containing raphides, which 

 serve as a more or less effective protection against the ravages 

 of animals. 



•Science. New. Ser. 1:119. 1895. 



1. Stahl. Pflanzen und Schnecken. p. 91. 1888. 



2. Moebius. Ueber den anatonilschen Bau den Orch.deenbiatter und dessen 

 Bedcutung f uer das System dieser Fanillie. 1887. 



3. Frank. Ueber die anatomische Bedeutuug und die Entstehung der vege(a- 

 bllischer Schleim. .Taliib. f. Wiss. Bot. 5:161. 1867. 



Hilgers. Ueber das Auftreten der Krystalle von oxalsaure Ka'lk ira Parenchyma 

 einiger Monocotylen. Jahrb. f. Wiss. Bot. «:285. 1867. 



Meyer. Ueber die Knollen der einheimischen Orchideen. Arch. d. Pliarm. 

 24:51. 1886. 



Schimper. Ueber Kalkoxalatbildung in den Laubbliitter. Bot. Ztg. 65,81,67,113 

 129, 145. 1888. 



