196 



establish tlic superposition of tlie mottled sandstones to tlie 

 slates. The basal part was made up of sub-angular gravel, o£ 

 which the auriferous cement rock of Humbug Scrub was an 

 example. These, continued the Professor, were considered to- 

 be of lluviatile origin, and might be the terrestrial equivalents 

 of the marine Miocenes seen at Government House quarry and 

 Hallett's Cove. With the exception of a few shrubs, the large 

 majority of the very varied plant species found in the neigh- 

 bourhood were, in regard to duration, ephemeral. This seemed 

 to be owing not so much to the quality of the soil as to its non- 

 retentive property for water, and consequently there could 

 only be exuberance of vegetable life when the surface was 

 saturated. Prom these circumstances the greatest richness 

 was about the margin of these Tertiary patches, and it was 

 there chiefly that search for orchids would be directed. 



The party then moved off in a southerly direction, and com- 

 menced to make their floral collections. This they experienced 

 no difficulty in doing, as flowers were to be seen in great pro- 

 fusion wherever the eye turned. Although not the orchid- 

 ground proper, yet some of these lovely flowers (chiefly the 

 Caladenias) were gathered on this scrub laud. That very 

 beautiful dark-blue flower Chaemascilla corymhosa was also met 

 with here. Ere long a sharp turn to the left was taken in order 

 to reach the edges of the Tertiary patches, where Prof. Tate 

 had indicated that orchids would be found. Such indeed 

 proved to be the case, and several varieties were secured, viz., 

 Thelymitra aristata (or midd), T. longifoJia, T. ^IcKihhinii, T. 

 antennifera, and last, but by no means least, T. grandis, which 

 a,ttains a height of three feet, with a spike of numerous flowers, 

 which is seldom less than twelve inches in length. Of Cala- 

 denias the following were observed : — C. Menziesii and C. Pat- 

 tersoni, with two or more of its sub-species. Other orchids 

 collected comprised Prasophyllum patens (or fusciim), with its 

 small white flowers; 2Iicroiis porrifolia (small green), Glos- 

 sodia major, the flowers of which are of a purple colour. 



Leaving the orchid ground, a course was struck for the 

 aqueduct coming from the Torrens weir. On the way a dis- 

 covery of an interesting little plant was made. This was 

 CaJocepliahis Drummondii, a Western Australian species, but 

 found in a few localities in this colony, its discovery in the 

 latter having been made by Professor Tate at Highbury. The 

 main road was now struck, and shortly afterwards the coach 

 was reached. 



The following are some of the plants found on this excursion, 

 viz.: — Dicliopogon strictus, Briinonia aiistralis, with its bright 

 blue spiky heads, Chaemascilla corymhosa, Cheiranihera linearis 

 (dark blue), Lotus australis, JPimelea Jnrmilis, the thorny 



