ORCHIDS OF MADAGASCAR. 519 



This plant is nearly allied to A. calcarata, Thouars. It has a 

 few ovate leaves with rather long petioles, 4 inches in length by 

 nearly 1 in breadth. The scape is from 8 to 9 inches in length, 

 and is glabrous in its lower part ; but the rhachis of the spike is 

 hispid. The flowers are small, entirely but very minutely 

 pubescent, lilac ; the lip is spotted, apparently with darter purple, 

 and has several raised lines on the middle lobe. The petals and 

 sepals are flat and spreading. The spur is straight, parallel 

 with the ovary, and about half its length, slender, gradually 

 tapering away to the point, which ends in a small hook. The 

 anther-lobes are rather short and almost straight, so that 

 they project over the entrance to the spur ; between them 

 lies the rostellum, which is also straight, and of just the same 

 length. The stigmatic arms are short and knobbed ; they 

 project almost at right angles to the anther-lobe, and are, 

 when the column is placed in the usual position of an orchid 

 flower (*. e. with the lip downwards), above and to the side of the 

 apices of the anther. This is an interesting adaptation to suit 

 the position of the flower. In most cases where the lip is upper- 

 most, the point of attraction is not at the base of the labellum, 

 but at the base of the posticous sepal, which develops a spur and 

 functions as a lip, as in Disci. Here, however, a different plan 

 is pursued. An insect alighting on the vertical lip, would push 

 its proboscis into the spur, and in withdrawing it would remove 

 the pollinia. These, instead of falling forward towards the lip, 

 would, from their weight and position, fall in the opposite direc- 

 tion, which would bring them to a position above the apices of 

 the anther, in which position we find the stigmatic arms. As, 

 however, the arms are outside the anther, there must also be a 

 divergence of the caudicles, as there is in so many of the Hale- 

 narice. The caudicles are rather long, the gland narrow and 

 pointed, the pollinia black. 



Sattrium. 



The head-quarters of this genus is at the Cape. It is found 

 also in Tropical Africa and India. All the Madagascar species 

 are endemic. 



S. trtnervk, Lindley, Gen. $ Sp. Orch. PL p. 314. 



On dry grassy plains, Ankafana, Imcrina, Beans Cowan ! ; in 

 pratis siccis, Jan. 1881, no. 3872 Hildebrandt\ in Herb. Brit. 



LINN. JOITRN.— BOTANY, VOL. XXI. 2 P 



