206 MR. P. GROOM—CONTRIBUTIONS TO THE 
the air. In the holosaprophyte the flower-bearing axes alone 
emerge from the nidus in which the plant rests. Even in Cory- 
santhes one sees that the major portion of the plant is concealed 
in the mass of decaying vegetable matter in which it grows; 
only one foliage-leaf and a flower are freely exposed to the light. 
In a later paper I shall show that in green Burmannias there is 
an analogous peculiarity. 
2. The next point of interest concerns the different modes in 
which absorbing-organs are formed, and their various shapes. In 
some forms the roots alone (or almost alone) absorb (Galeola 
javanica, Lecanorchis malaccensis, Aphyllorchis pallida). In 
others it is the subterranean parts of the shoot which take in 
nutritive solutions ; whilst the root-system is absent (Epipogum, 
Corallorhiza, or may (?) be represented by an organ mainly 
functioning as a food-reservoir (tuber of Corysanthes). 
The form of the absorbing-roots varies considerably. Galeola 
javanica has a close tuft of relatively short, thick, fleshy, un- 
branched roots which are inserted on a small rhizome. Lecan- 
orchis malaccensis and Aphyllorchis pallida have longer, more 
slender, feebly branched or unbranched roots which are attached 
to an elongated straight rhizome. 
The. histology of the external layers of the absorbing roots also 
displays considerable differences in the several plants. In Galeola 
javanica an irregular covering of cells with thick suberized walls 
coats the roots ; the development of root-hairs is reduced to a 
minimum the few hairs present being short and broad. <Aphyll- 
orchis pallida has more numerous root-hairs, which are further- 
more normalin shape. On the other hand, Lecanorchis malac- 
censis possesses a persistent external layer (corresponding to the 
piliferous layer) which is hairless but assumes the form of a 
modified velamen. It is interesting to note that in the terres- 
trial green orchid Spiranthes australis the roots have a persistent 
piliferous layer, some of the cells of which grow out into very 
long root-hairs, whilst others have their external walls cuticula- 
rized and their lateral and inner walls marked with reticulate 
thickenings of cellulose. The roots of Spiranthes and Lecan- 
orchis seem to show that in Orchidacew the evolution of the 
velamen was not a matter of great difficulty ; for it is fore- 
shadowed in these terrestrial plants. 
Usually in holosaprophytes there is a dwindling of root-hairs on 
roots (see Johow, cited on p. 213) ; it is otherwise with absorbing- 
