LEAVITT: TRICHOMES OF ROOT. 
277 
Dianella coerulea , I). revoluta, Funhid c-vata, Hyacinthus 
amethystinus, Lilium longiflormn , L. speciosum, Muscari 
Argaei , Xanthorrhoea arborea, Xerotes longifolia. 
Convallariaceae : Aspidistra lurida, Cordyline stricta, Dracaena 
nutans , D. hybrid, Polygonatum biflorum, Yucca angustifolia. 
Amaryllidaceae : Amaryllis amethystinus , JEucharis amazonica, 
Hypoxis erecta, Leucojum autumnale , Pancratium ovatum. 
Bromeliaceae : Billbergia Ijeopoldii, B. Quesneliana, Nidularium 
argenteum , Tillandsia Lindenii. 
Iridaceae : Freesia refracta , TWs Histrio , Z jyseudacorus , Zcm sp., 
Moraea JRobinsoniana , Sisyrinchium atlanticum , TB/isoma 
Ardernei. 
The tegumentary tissues of the root were carefully examined and 
described by Juel for a large number of the Liliillorae representing 
42 genera. He makes no mention of specialized hair-cells in this 
group, although he noted several instances in other groups. This 
negative evidence is in agreement with my own observations. In 
the Liliillorae in general the trichomes are of the unspecialized type. 
Gynandrae. 
The trichomes are sometimes predetermined, as in Pogonia 
ophioglossoides and other species mentioned below; but in many 
and probably in most of the Orchidaceae, any cell of the external 
layer may put out a root-hair as in Goody era tesselata , Liparis 
Loeselii , Odontoglossum luteo-purpureum , Selenipedium Sedenii , 
Vanda tricolor , and Vanilla planifolia. In the Orchidaceae 
generally the tegumentary apparatus is highly modified. Of 
especial interest in connection with the occurrence of tricho- 
blasts in several terrestrial species, is the character of the exodermal 
layer in the species the roots of which are provided with a velamen. 
The exoderm as constituted in these members of the group will be 
considered in another place. 
Dicotyledons. 
The Dicotyledons, with the exception of a single aberrant group, 
the Nymphaeaceae, to be discussed later, agree among themselves in 
