LIST OF PLANTS COLLECTED OR OBSERVED. 509 



Palisade occurs in about two layers of cells on each leaf face, those 

 on the ventral face being somewhat more elongated, and is much inter- 

 rupted on both faces by the hypostomatal air chambers. The chlo- 

 renchyma of the interior of the leaf is shorter-celled, with numerous 

 intercellular spaces, but is not typical pneumatic tissue. 



The stems of this species, as described bylleering, 1 from cultivated 

 material, have very prominent stomata, chlorenchyma composed of 

 roundish cells rich in chlorophyll, and strands of collenchyma in the 

 salient angles. 



Senecio tomentosus Michx. 



Cleared land (noncultural), Herbaceous formation, inhabiting moist 

 open ground. 



Leaves (especially the radical), nearly vertical, approximately iso- 

 lateral, arachnoid-tomentous, especially when young. 



Epidermis: Ventral, cells large, the walls not undulate; cuticle 

 roughened. Dorsal, cell walls thinner, undulate. Stomata some- 

 what more numerous on the dorsal surface, large, lying in all direc- 

 tions, level with the surface, each bordered by three to five (mostly 

 four) undifferentiated epidermis cells. Hairs weak, flexuous, blunt- 

 pointed, thin-walled, with slightly roughened cuticle, unicellular, 

 more abundant on the lower than the upper surface (especially in 

 older leaves). 



Chlorenchyma homogeneous, with no well-differentiated palisade. 



Midvein prominent beneath, composed of several (usually four) 

 mestome bundles, of which one, in the material examined, had its 

 greatest transverse diameter at right angles to the leaf surface. Bun- 

 dles bicollateral, perilept omatic (the leptome almost entirely surround- 

 ing the hadrome, but much more strongly developed on one side), 

 separated from each other and from the epidermis by much colorless, 

 thin-walled parenchyma, Stereome groups adjoining the leptome 

 usually on both sides of the bundle, but much stronger on the side 

 where the leptome is most developed. Hypodermal eollenchymatic 

 tissue in several layers beneath the midvein. Hypodermal collen- 

 chyma in the leaf margins. 



LIST OF THE PLANTS COLLECTED OR OBSERVED. 



The species enumerated in the following list were collected within 

 the limits of the Dismal Swamp region as above denned, with the 

 exception of a considerable number which were obtained near New- 

 bern, N. C, and which are included for the sake of recording their 

 occurrence at that station. Where the specimen was collected in 

 North Carolina, the name of the State is given with the station. 

 Where this is omitted, the station is understood to be in Virginia. 

 Species of which specimens were collected are so denoted by the col- 

 lection number; others here recorded are such as were carefully noted 



1 Engler's Bot. jahrb., vol. 27, p. 457. 1899. 



