114 RELATIONS OF SAPROPHYTES TO THEIK NUTRIENT SUBSTRATUM. 



Epipogium, aphyllu'n, as well as that of the " Coral-root", which is c-utirely destitute 

 of roots, develop fascicles of absorptive cells on their ramitications, and on special 

 little swellings; and the white subterranean stem structures of Bartsia alpina are 

 also provided with long absorptive cells. The white, fusiform, tuberously thickened, 

 underground stems of the Alpine Enchanter's Nightshade (Circcea alj?ina) exhibit 

 no roots during autumn and wintei-, nor until such time as new leafy stems sprout 

 from them and lift themselves into the daylight; they only have scattered club- 

 shaped absorptive cells. Yet it is inconceivable that the few absorptive cells meet 

 the entire requirements of these plants at the season of the development of stems 

 above ground. Food is absorbed in these cases also by the epidermal cells of the 

 entire tuber, underground stem, or coral-like rhizome, as the case may be. The 

 epidermal cells of these subterranean caulomes which lie immediately in contact 

 with the black mould or humus on the ground of forests, have such thin and tender 

 walls that they are quite as well adapted to the absorption of nutriment as are the 

 projecting absorptive cells; indeed the club-shaped absorptive cells on the small 

 tubers of Enchanter's Nightshade exhibit somewhat thicker walls than those 

 forming the general epidermis of the tubers. 



We may compare food-absorption as performed by these coral-like and tuberous 

 structures, imbedded in decaying plant residues, with the action of tape-worms in 

 process of sucking in through their entire epidermis the fluid filling the intestines 

 they inhabit. The epidermal cells of the thick tortuous root-fibres of Neottia 

 Nidus-avis are all capable of absorbing nutriment, though they do not project as 

 tubes, but are tabular, and have their outer walls, which are in immediate contact 

 with the nutrient soil, only slightly arched outwards (see fig. 16 ^). The green leafj^ 

 orchids rooted in the vegetable mould of woods and meadows are, on the contrary, 

 furnished with very long tubular absorption cells; and these cells do not wither 

 and collapse forthwith when the root elongates, but long retain their vigour and 

 activity. Whereas in the case of land plants adapted to mineral food-salts, the 

 tubular absorption cells ("root-hairs") are limited to a narrow zone behind the 

 growing point of the root and always die comparatively soon; in the case of orchids, 

 having cylindrical roots imbedded in vegetable mould, these structures appear to be 

 beset from end to end with long scattered tubular absorption cells, which ai-e 

 retained even through the drought of summer or the frost )f winter right into the 

 next period of vegetative activity; and these cells occur most abundantly in parts of 

 the ground where there happens to be a bed of humus or mouldering remains 

 particularly amenable to their purpose. Similar relations are found to exist in the 

 case of the dichotomously-branched roots of the Club-moss. They are twisted in 

 spirals and boi-e into the vegetable mould like corkscrews, and their absorption 

 cells form in some places regular tassels, which are completely cemented over with 

 fine black mould. The roots of grasses which, like the Mat-grass, live on the 

 decomposition-products of vegetable mould, are also distinguished by strikingly 

 long absorption cells, which grow in black or brown humus and there undergo the 

 strangest bends and contortions. When, for instance, a fragment of a dead root or 



