PLANTS WITH TRAPS AND PITFALLS TO ENSNARE ANIMALS. 



137 



Lathrcea passes its existence is often drenched through with moisture in the 

 immediate neighbourhood of the plant. A water-excreting function lias long been 

 attributed to the chambered leaves of the rhizomes. That such is the case has 

 been demonstrated by forcing water under pressure through the cut ends of the 

 rhizomes, when streams gush forth from the basal orifices of the leaves. In this 



Fig. 25.— Glandular structures in the Toothwort, Bartsia, and Butterwort. 



iPiece of an underground leaf-shoot of the Toothwort. ^Longitudinal section through the same; x2. s Longitudinal section 

 tlirough one of these underground leaves; x60. ^ Piece of the wall of a cavity; x200. s Subterranean bud of Bartsia; 

 natural size. 6 Cross-section through part of this bud; x60. 7 The margin of a bud-scale in section; x200. spieceofthe 

 epidermis of a leaf of Butterwort; x 180. 9 Transverse section through the leaf of a Butterwort {Pinguicula alpina); x 50. 

 10 Transverse section through Butterwort leaf; natural size. 



instance it is uncertain whether the stalked or the cushion glands assist in tliis 

 excretion, though from the minute details of their structure it would seem probable 

 that it is the latter. On any other hypothesis it is difficult to understand the 

 meaning of the pore on the summit. The matter has, however, been placed beyond 

 doubt by experiments on other allied plants, as, for instance, the Lousewort (Pedicu- 

 laris palustris), in which the glands are more easily kept under observation. We 

 have apparently in these gland-bearing chambers of Lathrcea a water-excreting 

 mechanism for the elimination of the surplus moisture, which in most plants is 

 transpired or evaporated into the air. Lathrcea being almost wholly subterranean 



