1883-84] Edinburgh Natiii'alists' Field Clitb. 155 



with the object. At the same time, a remarkable movement of the 

 protoplasm takes place, first Avithin the cells of the glands and then 

 within those of the pedicels. This movement Darwin calls " aggrega- 

 tion." When this takes place the cells present a difierent appearance. 

 Instead of being filled with a homogeneous purple fluid, they now 

 contain variously shaped masses of purple matter suspended in a 

 colourless or almost colourless fluid. The secretion appears to possess, 

 like the gastric juice of the higher animals, some antiseptic power. 

 During warm weather Darwin placed two ecpial-sized bits of raw 

 meat, one on a leaf and tlie other on wet moss. After fort^'^-eight 

 hours, that on the moss swarmed with infusoria, while that on the 

 leaf was quite free from them. Small cubes of albumen placed in 

 similar circumstances showed that those placed on the moss became 

 threaded with mould, while those on the leaves remained clear, and 

 were changed into a transparent jellj'. 



Although the leaves appear at a glance to be of a reddish colour, 

 they nevertheless contain chlorophyll in their petioles, both surfaces 

 of the blade, and the pedicels of the tentacles, so that they are able 

 to decompose the carbonic acid of the air ; but owing to their feeble 

 root-development, the plants would not be able to obtain a sufficient 

 supply of nitrogen if they had not the power of obtaining that 

 important element from captured insects. Many plants entrap insects 

 without apparently deriving any benefit — e. g., the sticky buds of 

 Horse-chestnut and the leaves of Saxifraga tridactylites ; but Francis 

 Darwin has proved beyond doubt that Drosera derives benefit from 

 the insects which it captures. He grew two lots of plants under 

 similar conditions : one lot he fed with nitrogenous substances, while 

 from the other all such material was carefully excluded. The number 

 of seeds produced by the fed plants was as 240 to 100 of the unfed 

 ones; Avhile the Aveight was as 380 to 100. The number and Aveight 

 of the flower-stalks and seed-capsules Avere also in favour of the 

 fed plants. 



DiON/BA. 



Dion»a muscipula is confined to the eastern part of North Carolina, 

 where it inhabits damp situations. From the rapidity with Avhich it 

 closes its leaves, it has received the name of " Venus's Fly-trap." 

 The leaf-blade is bilobed, and the petiole is foliaceous. The lobes of 

 the blade stand at rather less than a right angle to each other, and 

 the edges are set round Avith bristle-like projections, Avhich interlace 

 like the teeth of a rat-trap Avhen the leaf closes. The upper surface 

 of each lobe, toAvards the midrib, is thickly covered Avith minute red 

 glands, Avhich give it a rosy appearance, and the lobe also bears three 

 erect sensitive filaments arranged in a triangular manner. The fila- 

 ments are further provided Avith a joint or hinge near the base, so 

 that Avhen the leaf closes they fold doAvn, and thus escape injury. 



