DROSERA FILIFORMIS. [Chap. XIL 



of the genus this latter stimulus is the least effective of any. Par- 

 ticles of gla.s8, cork, and coal-c-inders, were placed on the glands of 

 six tentacles; and one alone moved after an interval of 2 hrs. 3U m. 

 Nevertheless, two glands were extremely sensitive to very small 

 doses of the nitrate of ammonia, namely to about ^ of a minim of 

 a solution (one part to 5250 of water), containing only Trhjsv o' 

 a grain (.000502 mg.) of the salt. Fragments of Hies were placed 

 on two leaves near their tips, which became incurved in 15 hrs. A 

 fly was also placed in the middle of the leaf; in a few hours the 

 tentacles on each side embraced it, and in 8 hrs. the whole leaf 

 directly beneath the fly was a little bent transversely. Uy the 

 next morning, after 23 hrs., the leaf was curled so completely over 

 that the apex rested on the upper end of the footstalk. In no case 

 did the sides of the leaves become inflected. A crushed fly wa 

 placed on the foliaceous footstalk, but produced no elTect. 



Drosera spathtilata (sent to me by Dr. Hooker). I made only 

 a few observations on this Australian species, which has long, nar- 

 row leaves, gradually widening towards their tips. The glands of 

 the extreme marginal tentacles are elongated and difl'er from the 

 others, as in the case of Drosera rotundifolia. A fly was placed on 

 a leaf, and in 18 hrs. it was embraced by the adjoining tentacles. 

 Gum-water dropped on several leaves produced no effect. A frag- 

 ment of a leaf was immersed in a few drops of a solution of one 

 part of carbonate of ammonia to 140 of water; all the glands were 

 instantly blackened ; the process of aggregation could be seen 

 travelling rapidly down the cells of the tentacles; and the granules 

 of protoplasm soon united into spheres and variously shaped 

 masses, which displayed the usual movements. Half a minim of a 

 solution of one part of nitrate of ammonia to 146 of water was 

 next placed on the centre of a leaf; after hrs. some marginal ten- 

 tacles on both sides were inflected, and after 9 hrs. they met in 

 the centre. The lateral edges of the leaf also became incurved, so 

 that it formed a half-cylinder; but the apex of the leaf in none of 

 my few trials was inflected. The above dose of the nitrate (viz. j^ 

 of a grain or .202 mg.) was too powerful, for in the course oif 23 hrs. 

 the leaf died. 



Drosera filiformis. This North American species grows in 

 such abundance in parts of New Jersey as almost to cover the 

 ground. It catches, according to Mrs. Treat,* an extraordinary 

 number of small and large insects, even great flies of the genus 

 Asilus, moths, and butterflies. The specimen which I examined, 

 sent me by Dr. Hooker, had thread-like leaves, from to 12 inches 

 in length, with the upper surface convex and the lower flat and 

 slightly channelled. The whole convex surface, down to the roots 

 for there is no distinct footstalk is covered with short gland- 

 bearing tentacles, those on the margins being the longest and re- 

 flexed. Bits of meat placed on the ^ands of some tentacles caused 

 them to be slightly inflected in 20 m. ; but the plant was not in a 

 vigorous state. After 6 hrs. they moved through an angle of 90, 

 and in 24 hrs. reached the centre. The surrounding tentacles by 



* ' American Natarallst/ Dec. 1878, p. 700i. 



