144 
Notes. 
same class possess one. Hence it has usually been assumed that aerial 
orchids acquired their velamen subsequently to their adoption of the 
epiphytic mode of life. But Schimper 1 , in his brilliant work on the 
epiphytes of South America, has pointed out that there exist epiphytic 
orchids which have no velamen, and terrestrial orchids which possess 
one. Hence it is quite possible that the terrestrial ancestors of an 
epiphytic orchid possessed a velamen. Schimper only discovered one 
epiphytic orchid which has no velamen ; it is a species of Stenoptera , 
which "grows in shady places on mossy or deeply furrowed bark. He 
found one purely terrestrial plant, Epidendrum cinnabarinum , which has 
a velamen. It may be pointed out that, with the exception of 
Schimper’s species, Stenoptera is a purely terrestrial genus, and 
the genera closely allied to it are likewise terrestrial. Hence it 
is more than probable that Schimper’s Stenoptera has only recently 
assumed its epiphytic mode of life ; and this becomes all the more 
likely when its habitat is considered. Epidendrum , on the other 
hand, is typically an epiphytic genus, and its close relations are all 
epiphytic. So it is a priori probable that E. cinnabarinum has changed 
from an epiphytic mode of life to a terrestrial one ; and in corrobora- 
tion of this view may be mentioned the occurrence of curious tufts of 
aerial roots, concerning the physiological significance of which 
Schimper could frame no suggestion. These aerial roots are probably 
relics of the epiphytic stage of existence of the plant, and are a sign of 
an extremely recent change to a terrestrial mode of life. 
It naturally suggested itself that light might be thrown on the 
question as to the date of origin of the velamen, by observations made, 
first, on orchids which naturally grow both as epiphytic and as 
terrestrial plants; secondly, on orchidaceous genera possessing both 
epiphytic and terrestrial species. During my stay in Singapore I had 
the inestimable advantage of Mr. H. N. Ridley’s advice as to the 
selection of suitable plants, and he suggested Grammatophyllum 
speciosum and species of Bromheadia for the purpose. 
Grammatophyllum speciosum. 
According to Ridley there are few orchids of which individual plants 
grow naturally both as terrestrial and as epiphytic plants : but of these 
few, Grammatophyllum speciosum is one. This plant can be found growing 
on the ground in the jungle when it has happened to fall off a tree — it is 
1 Schimper, Die epiphytische Vegetation Amerikas. Jena, 1888. 
