550 ON SEEDLINGS 



glaucous-green, spreading or arching, with the broadest face towards 

 the soil, and one on each side of the median ridge on the upper 

 surface, 9 mm. long. 



Stem woody, erect, glabrous, glaucous, obtusely three-ridged and 

 shallowly three-furrowed owing to the adherent or decurrent bases 

 of the leaves ; 1st internode undeveloped ; 2nd 5 mm. long ; 3rd 

 4-25 mm. ; 4th 5'25 mm. ; 5th 6 mm. ; 6th 5 mm. ; 7th 6 mm. ; 

 8th 5-5 mm. ; 9th 4 mm. 



The primary leaves are simple, entire, cauline, verticillate in 

 whorls of three, linear- subulate, acute, horizontal, compressed hori- 

 zontally, and convex on both surfaces, decurrent or adnate by their 

 faces to the stem, and covering the whole internodes with the free 

 part, 8-13-5 mm. long, deep glaucous-green above and paler beneath. 



Thuja gigantea, Nutt. (fig. 676). 



Primary root long, woody, flexuose, brown, with a few long 

 brownish fibres. 



Hypocotyl woody, erect or suberect, terete, about T5 cm. long, 

 1-5 mm. thick, brown. 



Cotyledons two. 



Stem woody, terete and smooth near the base, ridged higher up 

 from the decurrent sessile leaves, brownish-green. 



Leaves of two kinds, with intermediate stages. 



(a) Acicular leaves in more or less true whorls, decurrent except 

 the few lowest, which are only 2-3 mm. long by '75 mm. wide, 

 and yellowish-green, whilst the upper ones are 1 cm. long, 1-5 mm. 

 wide, prominently decurrent, sharply pointed, and dull dark green 

 above with a lighter tint and white midrib on the lower surface. 



After about a dozen pseudo-whorls, the first "branch is formed 

 and may or may not bear a few acicular leaves, passing gradually 

 or suddenly into the second predominating form. 



(b] Scale-like, imbricate leaves as in Thujopsis dolabrata, &c. 1 



Thuja occidentalis, 2 L. 



Primary root tapering downwards with a few fibrous lateral 

 rootlets. 



1 Tubeuf, 1. c. p. 103, figures and describes the same species and says of 

 the cotyledons, ' about 6 mm. long, and 1-1-5 mm. wide, broadly pointed, 

 green on both surfaces, midrib scarcely visible.' He also (p. 102) figures and 

 describes Thuja japonica, which differs from T. gigantea in having broader 

 cotyledons, and the primary leaves in opposite decussate pairs. The seeds 

 of these two species are also described (p. 31). 



2 Cf. Tubeuf, 1. c. p. 101 (with figure of a very young seedling). The coty- 

 ledons are described as about 8 mm. long, by 1 mm. wide. 



