150 MR. P. GROOM—CONTRIBUTIONS TO THE 
and that of others on holosaprophytes belonging to Monocoty- 
ledons and to Dicotyledons. This summary may be briefly given 
here. 
1. There is a tendency for the root-system to diminish greatly 
in surface till roots may be entirely absent. But exceptions exist 
in all the monocotyledonous families ; for long fibrous roots may 
occur, or a close system of many short roots. 
2. The root-system, or the rhizome replacing it, often assumes 
a coral-like or stellate form. 
8. No fully-developed root-hairs occur in any saprophyte with 
the exception of Sciaphila Schwackeana. 
But hairs functioning as root-hairs are well developed on the 
rhizomes of Corallorhiza innata, Epipogum aphyllum, and Dictyo- 
stegia orobanchoides. 
4. As regards the outer layer which persists over the root, no 
general rule prevails. 
5. The cortex is greatly developed in the roots of all sapro- 
phytes, and is formed of cells in regular circles or radii. 
6. Concerning the endodermis, no general rule prevails. 
7. Pericycle is a distinct layer in monocotyledonous roots; 
but not so in the Dicotyledons. 
8. As regards the central eylinder: in all holosaprophytes, 
with the exception of Neottia nidus avis and Sciaphila caudata, 
deviations from the normal type occur. The modifications consist 
either in reduction in the vessels, or in a changed grouping 
in the xylem and phloém, or in incomplete differentiation of the 
procambium. 
9. Mycorhiza is present in all holosaprophytes excepting 
Wullschlegelia. 
10. The structural modifications in the shoot are not nearly so 
striking as those in the root. 
11. The epidermis of holosaprophytes has no stomata. But 
in Epipogum aphyllus the subterranean parts have stomata. 
In the cortex of the floral axis colouring-matters are usually 
present ; the intercellular spaces are small because of the absence 
of chlorophyll. 
The mechanical system of the floral axis is in all cases restricted 
to a general sheath of sclerenchyma, on the inner side of which 
the vascular bundles lie. 
The vascular bundles in the rhizome and floral axis are usually 
