110 



THE ECOLOGICAL RELATIONS OF ROOTS. 



IX. ECADS. 



During tihe course of these investigations, a number of species were 

 encountered and excavated in two or more different habitats. While 

 a few of these have already been described in explaining the root 

 habits of plants of the several plant communities, others have been 

 reserved for comparison in this place. Differences in ecads were 

 always determined by actual comparison of plant materials from the 

 two habitats at the same time, and these differences are expressed 

 wherever possible by means of photographs or drawings. Any personal 

 error was further checked out by the judgment of a second person, 

 no statements being made until there was a consensus of opinion. 



Smilacina stellata. — The shade form was excavated in a spruce-fir forest 24 

 feet from the brook bank and 3.5 feet above the water-level. The ground was 

 covered with about 0.5 inch of raw humus underlaid with about 2 inches of 

 well-decomposed humus mixed with sand. Below this was very moist sand 

 with gravel and rocks. The light value was only 0.02. 



The roots were much sparser and shorter, although somewhat greater in 

 diameter than those of the gravel-slide form (page 85). While an inch of the 

 rhizome of the latter form gave rise to 18 roots averaging 3.5 inches long, an 

 average inch of the shade rhizome showed 8 roots only about 1.5 inches in 

 length (plate 29, a) . The longer roots, which have their origin near the base of 

 the vertical stems, were Hkewise both fewer and shorter. In the gravel-sUde 

 form they varied from 2 to 5, in the shade form there was frequently none and 

 seldom more than 2. The maximum length of the latter was only 16 inches, 

 with an average length of about 11 inches; in the former case roots were 

 traced to 44 inches in depth, with an average depth of about 32 inches. An 

 intermediate stage was found in the fir forest, a habitat which has been shown 

 to be somewhat less meosphytic than the spruce. The roots were nearly as 

 sparse as those in the spruce forest but somewhat longer. 



Chamsenerium angustifolimn— This cosmopolitan plant is found in habitats 

 of all degrees of mesophytism, from the gravel-shde and bare bum to very 

 moist dark places in the spruce forest. A large group of these plants was 

 examined at the foot of a slope near a stream and 4 or 5 feet above water- 

 level. They were growing in the haK shade of Douglas fir and mountain 

 maple on one side. Below the first inch or two of duff and humus the soil 

 consisted of a rich black sand intermixed with gravel and rich in humus to a 

 depth of 2 or 3 feet. The plants are connected by means of strong, tough, 

 well-branched rhizomes from 5 mm. to more than 10 mm. in diameter. These 

 lie at depths varying from only 0.5 inch to 6 or 8 inches. The subterranean 

 portions of the erect stems are practially free from roots. At rather distant 

 intervals along the rhizomes, roots varying from 1 to 5 mm. in diameter 

 arise. Many of these pursue a more or less vertically downward course, with 

 but a few major branches, and reach depths of 35 to 48 inches (fig. 51). They 

 taper very gradually and are only fairly well clothed with small rootlets. 

 The latter usually occur in clusters of from 3 to 7 and are frequently less than 

 an inch long. In addition to these, however, other longer and abundantly 

 branched laterals supplement the absorbing system. These extend from 3 

 to 10 inches. Sometimes these deep roots break up into numerous branches, 

 all of which are similar to those aheady described. In addition to these larger 

 roots, the rootstock also gives rise to smaller, shallower, and frequently 



