188 Angewandte Botanik. 



Holm, T., Medicinal plants of North America. 8 7. Thuja 

 occidentaUs L. (Merck's Report XXIV. p. 28—30. f. 1 — 12. Febr. 

 1915.) 



All the leaves of the primary axis of the seedling are acicular, 

 spreading, and in whorls of three; in the axils of the, upper of these 

 leaves shoots develop which, however, bear only scale-like, oppo- 

 site, and appressed leaves similar to those of the mature tree. The 

 primary axis of the seedling is obtusely three-winged from the 

 decurrent leaves in whorls of three; in each wing is a wide resini- 

 terous duct, and a Strand of stereids. The middle portion of cortex 

 is broken down so as to form lacunae, while the innermost part 

 of cortex is solid, and contains a band of ducts which are much 

 narrower than the three peripheral, located in the wings. In the 

 Stele is a thinwalled parenchyma with two concentric bands of 

 stereids developed from cambium. The structure of the acicular 

 leaves of the seedling is dorsiventral with a ventral palisade-tissue 

 covering a very open pneumatic tissue; along the margins is a 

 hypoderm of a single Stratum of stereome; a resiniferous duct is 

 located beneath the midvein. In the scale-like leaves, on the other 

 hand, the palisade-tissue is located beneath the dorsal epidermis. 



Theo Holm. 



Holm, T., Medicinal plants of North America. 87a. Tsuga 

 Canadensis Carr. (Merck's Report XXIV. p. 59—60. f. 1 — 11. 

 March 1915.) 



Characteristic of Tsuga are the membranaceous, acute bracts 

 which are much shorter (at maturity) than the concave, loosely im- 

 bricated, woody cone scales. Seven species are known of the genus, 

 confined to temperate North America, and to eastern and 

 Southern Asia; on this continent two species occur in the eastern 

 part, two in the western. The name is the Japanese appellation of 

 the Hemlock tree. During the first season the twigs are hairy 

 from pointed, thickwalled, unicellular hairs; the secundary cortex 

 contains concentric bands of scattered stereids. The leaf structure is 

 dorsiventral; there is a layer of high palisade-cells on the ventral 

 face, beside that the midrib is surrounded by a wreath of typical 

 palisade cells borderingon a thinwalled parenchyma-sheath. Stereome 

 is poorly represented, and occurs as a few cells on the sides of the 

 duct, and in the margins; the stomata are confined to the dorsal 

 face of the blade, and epidermis is very thickwalled, and distinctlj^ 

 suberized. Theo Holm. 



Holm, T., Medicinal plants of North America. 88. Castayiea 

 dentata (Marsh) Borkh. and C. pumila (L.) Mill. (Merck's 

 Report. XXIV. p. 85—87. f. 1-13. April 1^15.) 



The drug Castanea is the dried leaves of C. dentata, collected 

 in Sept. or Oct., w^hile still green. De CandoUe considers the 

 American C. dentata a mere variety of C. vulgaris Lam. The seedling- 

 stage is described, and mycorrhizae appear already during the first 

 season; the primary shoot bears several alternate leaves, of which 

 the first one has the margin entire, while the succeeding show the 

 typical leaf-outline of the mature tree. In the primary root the 

 secondary cortex contains four concentric bands of thickwalled 

 stereome, somctimes mixed with sclereids. In the apical portion of 

 the twigs the phellogen arises in the hypodermal Stratum of cortex; 



