i 70 Shiv Ram Kashyap. — The Structure and Development of 
colour is brought to the laboratory and kept inside the room in very dim 
light with plenty of water, the new parts formed are yellowish green in 
colour and much more open than the older parts. The lobes also are 
longer, less broad, and more branched (Figs. 19, 23, 24, 2 6 ). This condition 
may be compared to etiolation in Flowering plants. 
A well-grown prothallus that has been growing for some months may 
be as much as 3 centimetres in diameter ; usually it is only 2 to 3 milli- 
metres in height, including the lobes. The smaller prothalli also are of 
about the same height, so that the height does not vary so much as the 
diameter. Usually a little less than one-half of the height is formed by the 
lower compact part of the prothallus, and it consists of 6 to 12 layers of 
cells. The rest of the height is formed by the projecting lobes (Fig. 23)- 
X&Q 
Text-fig. 23. 
In some cases, however, the lobes were found to be very small and the 
lower part of the usual thickness or much thicker (Fig. 25). In Fig. 25 the 
thickest part of the lower half below the lobes consisted of about twenty 
layers of cells. In very large prothalli the central part may die, and if the 
prothallus is lobed the lobes may become more or less separated and 
continue to grow independently for some time. It reminds one of the similar 
process in the Liverworts. 
Lastly, it may be mentioned that the prothallus is very often attacked 
by a fungus, often found in the upper cells of the lobes, though the cells at 
their base also may be sometimes affected. The fungus does not appear to do 
much harm : on the contrary, the prothalli seem to be flourishing vigorously. 
The contents of the affected cells are transformed into small and large brown 
globules, stained black with osmic acid. When stained with fuchsin-iodine 
green mixture, they take the green colour in preference to the fuchsin. 
The fungus multiplies by minute oval conidia formed in chains on erect 
