310 FRANCIS DARWIN. 



deals ■with the process as it occurs in the former of these 

 parts, where it is far more easily observed. 



The pedicel is composed of elongated cells of various 

 lengths and of about '016 mm. in breadth; the cells forming 

 the upper and middle portions are filled with a crimson 

 fluid (fig. 1), which is, however, absent from dwarf leaves 

 grown in very shady places (figs. 9 and 10), and is absent 

 from the lower cells of all the tentacles (fig. 8) . The proto- 

 plasmic currents which may be observed in the cells vary 

 much in complexity ; either flowing round the cell-walls as 

 described by my father;^ or forming a complicated flowing 

 network like that seen in the staminal hairs of Traclescantia, 

 &c. This netAVork is well seen in the tentacles of pale dwarfed 

 leaves which grow almost hidden in moss ; the current almost 

 invariably flows from one chlorophyll body to another (when 

 these are present), so that they are connected together by a 

 most beautiful moving network. In other cells the currents 

 are simpler as shown in figs. 1, 9, and 10. Neither my father 

 nor myself have ever been able to make out a nucleus ; and 

 this forms a markad distinction between the flowing network 

 of Drosera and that in the hairs of Traclescantia, Cucurhita, 

 &C.2 "Well-formed chlorophyll bodies are found in the lower 

 cells of the tentacle, in the middle cells they are dwarfed and 

 yellow and do not contain starch, in the extreme upper 

 cells close under the gland they are again found fairly de- 

 veloped. Highly refracting globules which appear to be 

 oil-drops are occasionally seen floating in the coloured fluid 

 and carried round by the currents. 



The change from the normal state to one of aggregation 

 is extremely striking; various forms and stages of aggre- 

 gation are shown in figs. 1, 2, 3, 6 and 7. Instead of con- 

 taining a homogeneous purple or crimson fluid the cells con- 

 tain variously shaped masses of crimson matter suspended 

 in almost colourless fluid. " The change is so conspicuous 

 that it is visible through a weak lens or sometimes by the 

 naked eye.^'^ The crimson masses are now seen to undergo 

 most remarkable changes both in form and position ; the ra- 

 pidity with which these changes occur varies with the nature 

 of the exciting cause and the stage of aggregation in which 

 the tentacle is ; sometimes the changes are only to be detected 

 by drawing a given mass and examining it after an interval of 

 several minutes ; in other cases they are so conspicuous as to 



1 'Insectivorous Plants,' p. 38. 



- According to Sachs ('Handbook,' p. 3S) the nucleus disappears when 

 the streaming commences in the sacs of the Characew. 

 » ' Insectivorous Plants/ p. 39. 



