> DROSERA 285 



with powdered black mustard, can be detected microscopically by 

 the palisade-stone cells, which become blood-red on heating with a 

 solution of hydrated chloral. 



DROSERACE-E, OR SUNDEW FAMILY 



A small family of biennial or perennial herbs which are very widely 

 distributed. In some respects these plants are among the most 

 interesting in the plant kingdom, being of very great biological 

 interest. It includes Dionsea muscipula or Venus' fly-trap, which is 

 found in the sandy bogs of a limited area in the vicinity of Wilming- 

 ton, N. C. It exhibits in a remarkable degree the irritability com- 

 mon to some plants; a slight touch to the sensitive hairs on the leaf 

 causes a rapid movement of the modified leaf-blade. For illustra- 

 tion of the plant consult Kraemer's Applied and Economic Botany, 

 p. 362. The typical genus of the family, Drosera, has about 110 

 species, which are most abundant in Australia, several species, how- 

 ever, being rather common in the United States. They all possess 

 peculiarly stalked glands, forming in Drosera the so-called glandular 

 tentacles, and of which there are 2 types (a) . those situated upon the 

 surface of the leaf possessing an ellipsoidal glandular head, and (6) 

 those occurring on the margins of the leaf in which the head has 

 the form of a spoon. 



DROSERA. Sundew. The entire plant of Drosera rotundifolia 

 or other closely allied species of Drosera (Fam. Droseracese). The 

 plant is collected at the time of flowering, the roots washed, the 

 lower withered and darkened leaves removed, and carefully dried. 



Description. More or less crumpled and matted; leaves petio- 

 late, mostly basal, except in submerged plants which have more or 

 less lengthened internodes ; laminae sub-orbicular or broadly elliptical, 

 7 to 15 mm. in diameter, abruptly narrowed into the petioles and 

 covered with numerous pinkish-red glandular tentacles, about 4 mm. 

 in length; petioles very slender, from 2 to 4 cm. in length and 0.5 to 

 2 mm. in diameter, somewhat flattened and pubescent; scapes fili- 

 form, from 5 to 10 cm. in length, having the flowers in a 1-sided 

 raceme-like inflorescence; flower buds about 5 mm. in length, having 

 an imbricated calyx and convoluted corolla; lower portion of the 

 stem somewhat flattened, tapering, from 5 to 30 mm. in length and 

 bearing a few very slender roots. 



Inner Structure. Glandular tentacles, from 0.250 to 0.400 mm. 

 in length, and consisting of a long multiseriate stalk traversed by a 

 strand of tracheids, which become broader on extending into the 



