PLANTS WITH TRAPS AND PITFALLS TO ENSNARE ANIMALS. 139 



arctic region and amongst the high mountain flora throughout almost the whole of 

 Europe, and is very striking owing to the colour of its foliage being a mixture 

 of black, violet, and green. The flower, too, is of a sombre dark-violet hue, and 

 the entire plant, by reason of this peculiar colouring, gives a truly funereal im- 

 pression. We may remark incidentally that the name Bartsia was chosen by 

 Linnaeus for this sad-hued plant as an expression of his own grief at the death 

 of the zealous naturalist and physician, Bartsch, who was his intimate friend, and 

 who succumbed at a comparatively early age to the climate of Guiana. Damp 

 black earth in the neighbourhood of springs constitutes the favourite habitat of 

 these plants. Upon digging in summer time down to their roots, one sees that 

 a few suckers proceed from them, and fasten upon the sedges and other plants 

 growing in the vicinity; but one also discovers subterranean shoots having "root- 

 hairs " developed near the nodes, at which are inserted the paired white scales; and 

 these "root-hairs" have the function of absorption-cells. Towards the autumn, oval 

 buds, likewise subterranean, are matured, in form not unlike horse-chestnut buds 

 (see fig. 25 6 ), and composed of etiolated scales arranged in four rows and over- 

 lapping one another like tiles, so that only the back of the upper part of each 

 scale is visible, the lower part being covered by the scale next beneath it. 



On the visible part of each scale's convex under surface three sharply projecting 

 ribs are noticeable near the middle, whilst the two margins are rolled back so as 

 to form a recess in each case. But, as may be seen in the cross-section of a Bartsia 

 bud (see fig. 25 7 ), one pair of scales lies over the next higher pair in such a way as 

 to convert the recesses into ducts. Owing to this construction the interior of the 

 bud is perforated by twice as many ducts as there are covered leaf-scales, and the 

 orifices of each pair of ducts occur at the spots where the evolute margins of one 

 scale begin to be covered by the middle of the next lower scale. On one wall of 

 the ducts, i.e. in the recesses, structures like those which occur in the cavities of 

 Lathrcea are developed, i.e. stalked glands, each composed of two cells borne upon 

 a basal cell; secondly, pairs of hemispherical domed cells; and, lastly, ordinary flat 

 epidermal cells (see fig. 25 8 ). There can be little doubt that the whole apparatus 

 acts in the same way as in Lathroea, and is adapted to the capture of Infusoria. 



The subterranean buds of Bartsia, just described, are produced late in the sum- 

 mer, and aerial shoots arise from them in the course of the following spring; and 

 seeing that the foliage-leaves on these shoots are richly furnished with chlorophyll, 

 and manufacture organic compounds in the sunlight from the constituents of the 

 air and from the fluids imbibed by absorption-cells from the ground, the question 

 arises whether an additional supply of nutriment from the dead bodies of captured 

 animals can be necessary or even advantageous. We shall, however, taking into 

 account the circumstances of Bartsia alpina when growing wild, answer this 

 question with an unconditional affirmative. The plant belongs, as has been said, 

 to an arctic and high alpine flora, and grows in regions where the activity of 

 plants above ground is limited to the short period of two months. After the lapse 

 of this brief vegetative season, the aerial parts of arctic and alpine plants either 



