366 WILLIS : MORPHOLOGY OP THE PODOSTEMACEÆ 
The thalliis in the creeping form, with which we shall 
first deal, is like that of Dicræa stylosa in transverse section, 
and grows in the same way by tangential divisions of its 
cortical cells. It may be as much as 1 cm. wide, and creeps 
along the rock, closely attached to it by root-hairs and 
occasional hapterous outgrowths, branching exogenously, 
till at last a large plant like that figured in the left hand of 
PI. XXV. may arise. At intervals of a few millimetres 
along the upper side of the margins the secondary shoots 
arise as seen in the figures, and endogenously as usual ; 
their first appearance is extremely close to the growing apex. 
These shoots are very like those of a Dicræa, but are often 
rather more prostrate, with distichous sheathing leaves to 
about 5 mm. long. As the figure indicates, these leaves 
probably only perform a small portion of the work of 
assimilation, being small, as in Dicræa, in proportion to the 
area of the thallus. Vascular bundles lead from the main 
bundle of the thallus to the leafy shoots, in the ordinary 
way, and the thallus grows in thickness like that of Dicræa 
by tangential division of the cortex. 
We may now go on to deal with the extraordinary series 
of forms shown in Pis. XXV, and XXVI. All in XXV. and 
the left-hand half of XXVI. are the var. Willisiana collected 
by Mr. Barber, while the rest are some forms collected near 
Atgaon. These are not the only Atgaon forms, but are those 
not well represented in the Kanara material. The cup and 
disc forms are frequent at Atgaon, but not the simple 
creeping form. 
Not infrequently, as in some of the plants on XXV., 2, and 
in XXVI., 5, 6, the creeping form, instead of growing to a 
large size, remains short,* and more or less discoid orlobed. 
When the growth of the actual apices is not much faster 
than that of the tissue between, the form approximates to a 
* I am inclined to think that the large creeping form may perhaps be 
varietally distinct from the small one, though they agree very closely 
indeed in all other points than size ; the question can only be settled by 
detailed study on the spot where they grow. 
