42 Osborn. — Some Observations on Isoetes Drummondii , A.Br. 
until in January and February it may be little more than 0*5 in. per month. 
The dry season extends from November to March, during which time the 
vegetative activity of all small herbaceous plants is at a standstill, the 
temperatures high, the in- 
solation often intense, and 
the soil baked hard. It is 
not usually until the close 
of May that, after several 
periods of heavy rainfall, the 
soil becomes thoroughly 
saturated and perennial 
herbs make their ap- 
pearance. 
The vegetative period 
for Isoetes Drummondii ex- 
tends from the end of May 
or the beginning of June 
to November. During this 
time the plant forms a small 
rosette of from eight to 
twenty linear terete leaves, 
bright green and rather dia- 
phanous, through which the 
septa of the four air-canals 
can be seen. Below ground 
the leaves collectively form 
a slightly bulbous structure 
(Fig. i) composed of their 
closely imbricate, wide, 
membranous bases. This 
bulb-like base is colour- 
less, and arises from a small 
„trilobed stock which is 
buried about 2 cm. below 
the surface of the soil. The 
stock bears a number of 
colourless bifurcating roots 
arising from the three 
grooves. Numerous brown 
withered roots are found 
season. Two lobes and the groove between them are visible. 
Each lobe bears withered roots of the previous growing 
season; the functional roots issue from the groove. The 
lobe to the right bears the older portion as a * cap ; partially 
detached. 
on the lower surface of the lobes, but it is noticeable that the upper leaf- 
bearing surface has no remains of old sporophylls upon it (Fig. 2). With 
the advent of the dry season the leaves become yellow and rapidly wither ; 
