Dr. James MACBRiDr. on Sarracenia adunca. 49 



and fiills to the bottom of the tube, where it is either drowned, or 

 attempts in vain to ascend against the points of the hairs. The 

 fly seldom takes wing in its fall and escapes; but this sometimes 

 happens, especially where the hood has been removed to assist 

 observation. In a house much infested by flies, this entrapment 

 goes on so rapidly that a tube is filled in a few hours, and it be- 

 comes necessary to add water, the natural quantity being insuf- 

 ficient to drown the imprisoned insects. The leaves of the 

 S. adunca and S. rubra of Walter might well be emplo3'ed as fly- 

 catchers ; indeed I am credibly informed they are in some neigh- 

 bourhoods. The leaves of ihejlava, although they are very capa- 

 cious, and often grow to the height of three feet or more, are never 

 found to contain so many insects as the leaves of the species 

 above mentioned. The spreading fauces and erect appendices 

 of the leaves of this species render them (1 suppose) less destruc- 

 tive. 



The cause which attracts flies is evidently a sweet viscid sub- 

 stance*, resembling honey, secreted by, or exuding from, the in- 

 ternal surface of the tube. On splitting a leaf it may readily be 

 discovered in front, just below the margin, and in greatest quan- 

 tity at the termination of the ala ventralis. From the margin, 

 where it commences, it does not extend lower than one-fourth of 

 an inch. During the vernal and summer months it is very per- 

 ceptible to the eye and touch ; and although it may be sonietiraes 

 not discoverable by either, yet the sensation of sweetness is rea- 

 dily perceived on applying the tongue to this portion of surface. 

 In warm and dry weather it becomes inspissated, resembling a 

 whitish membrane. 



* This substance it seems was noticed by Bartrarn the younger (see the Preface to his 

 Travels). I was entirely ignorant of his conjectures respecting it, until long aftef I had 

 proved their correctness. 



VOL. XII. H The 



