82 
G. P. DARNELL-SMITH ON 
In a plant like Psilotum, the sporophyte of which requires an especial environment, 
it is of the greatest importance that the spores should not germinate until they have 
reached a suitable locality, otherwise the result of the whole sexual process would be 
rendered nugatory ; and it is probably their refusal to germinate, under any conditions 
that would be adverse to the sporophyte, that has so long delayed the life-history of 
the gametophyte being described. They have ceased to show any great amount of 
adaptability, and it is questionable whether the adaptability of the gametophyte 
among the Pteridophytes is so general as has been supposed. 
Thus Dr Lang * holds the view that the importance to the species in the 
vascular cryptogams of satisfactory adaptation of the gametophyte to its environment 
can hardly be overestimated. For the establishment of the sporophyte in a new 
situation is entirely dependent on the gametophyte having been able to come to 
maturity and produce sexual organs, so that the localities of the plants are deter- 
mined more by their suitability for the gametophyte than for the sporophyte, except 
in so far as the latter is spread by vegetative propagation.” 
So frequently did I find Psilotum growing in connection with the iron deposits 
previously described, that I suspected iron might be an element necessary for its 
development. To test this, a number of Psilotum rhizomes were collected, washed 
thoroughly free from adhering soil, dried, calcined, and the ash tested for iron ; this 
element, however, was not detected. 
While Psilotum has been found most abundantly near the sea-coast in the 
neighbourhood of Sydney, I have, nevertheless, found it growing vigorously fifty 
miles inland. 
Note on the Chemical Constitution of Hawkesbury Sandstone. 
Appended are the results of six analyses of Hawkesbury sandstones, for which J am indebted to 
Mr W. G. Card, Curator of the Geological Museum, Sydney. 
Analysis of Sydney Sandstone. 
Greens Q, 
Annandale. 
Saunders, 
Pyrmont. 
Purgatory, 
Pyrmont. 
Regans, 
Waverley. 
Phippards, 
Waverley. 
Undercliffe, 
Tempe. 
H 2 0- . 
h;o+ . 
Si0 2 (free) 
Si0 2 (comb) 
ai 2 o 3 f . 
Fe 2 0 3 . . ' 
FeO . 
MnO. 
CaO . . . 
MgO. . . 
k 2 o . . . 
Na„0 
so 3 . 
co 2 . 
Ti0 2 . 
0-94 
2-50 
66-35 
12-40 
10-93 
o-io 
2-48 
0-08 
0-16 
0- 52 
1- 58 
0-21 
Trace 
1-61 
0-51 
0-68 
1-80 
72-70 
9-35 
9-20 
0- 50 
1- 92 
0-05 
0-22 
0- 39 
1- 50 
0-16 
Trace 
1-34 
0-35 
0- 33 
1- 05 
83-55 
5- 30 
6- 01 
0- io 
1- 37 
0-04 
0-08 
0-25 
0-81 
o-oi 
Trace 
0-84 
0-66 
0-40 
0-98 
80-50 
6-25 
6-12 
0- 30 
1- 92 
0-06 
0-20 
0- 36 
1- 14 
0- 15 
Trace 
1- 29 
0-69 
0- 49 
1- 41 
77-20 
7- 55 
8- 16 
0- 41 
1- 56 
0-04 
0-18 
0- 36 
1- 50 
0-06 
Trace 
1-16 
0-36 
2"56 
| 81-80 
9-90 
0- 30 
2-07 
oil 
0T5 
1- 45 
0T8 
None 
1-14 
0-05 
100-37 
100-16 
100-40 
100-36 
100-44 
9980 
* W. H. Lang, “ The Prothallus of Lycopodium clavatum,” Annals of Botany, xvii, p. 311. f Includes P 2 0 5 . 
