52 Osborn. — Some Observations on Isoetes Drummondii , A.Br. 
their attachment to the parenchyma of the sporophyll, and from each other 
along the lines of weakness already noticed in the side of the wall. They 
rapidly roll upwards, inside out. Once the process of tearing away has 
begun it proceeds very quickly, and in a few seconds the whole sporangium 
wall has rolled back upon itself in a tight coil. Some of the spores are 
carried back with it, but the main mass is left in situ in the depression at 
the base of the sporophyll. Great numbers of megaspores and microspores 
are thus set free upon the break up of a sporophyll mass within a few square 
centimetres. 
The opening of the sporangia has been followed many times in the 
laboratory by bringing ripe dry sporophylls there and allowing them to 
absorb moisture. That the process depends upon differences in tension 
Fig. 13. Single cell of mucilage tissue, with walls fully extended with water. From fresh 
material collected in June at time of the sporophylls being elevated, x 173. 
Figs. 14 a and 1.4 b. Single microsporophyll removed from dry mass of bases and sporangia found 
on surface of soil in June. x 3. 14 a shows abaxial view; at top of shield withered remains of 
lamina is seen, at base an irregular lump of dry mucilage. 14 b shows adaxial surface, the elongate 
flat-topped sporangium still in place. 
Fig. 15. Sporangium wall in surface view, after it has torn away from sporophyll, showing 
fimbriated segments into which side of wall has torn. 
between the inner and outer surfaces of the wall consequent upon the 
absorption of water can be shown by placing the freed, rolled-up sporangium 
wall in different strengths of a dehydrating solution such as alcohol. 
A solution of 70-80 per cent, causes the wall to unroll and float in the 
liquid like a membrane (Fig. 15), roughly star-shaped, with truncated 
points. Stronger alcohol causes the membrane to close back into its 
original position before tearing open. The same sporangium wall can be 
made to repeat the process several times by varying the proportions of 
alcohol and water in which it is placed. 
Conclusion. 
It is not the purpose of this paper to enter into a general discussion 
of the morphology of Isoetes. So far as the stock is concerned, the chief 
