272 TlMEHRI. 



hood-like flowers and plump pseudo-bulbs. Catasetum 

 macrocarpum (tridentatum) has made a leap upwards and 

 lodged itself in the lower branches of trees, often just 

 above the surface of the creek or swamp, while Catase- 

 tum longifolium has got to the top of the eta palm and 

 settled under its crown. In habit these three species 

 are very similar, the pseudo-bulbs being in each case 

 retained, the differences mainly consisting in the flowers. 

 In Oncidium however we have no species now living on 

 the sand, but we can easily conceive that it commenced 

 with a plant something like a Cyrtopodium, which genus 

 contains the largest sand orchids in Guiana. The first 

 step now visible is exemplified by Oncidium altissimum, 

 a plant with large pseudo-bulbs and rather thin leaves, 

 and culminates in Oncidium Lanceanum, the species so 

 well known in Georgetown. Because the latter climbed 

 highest and got into the sunlight, it became able to bear 

 the drying winds of our city streets and illustrate 

 the survival of the fittest from several points of view. 



All the species which climbed from the sand have 

 their pseudo-bulbs immediately above the tangle of roofs, 

 and their flowers issuing from beneath these or at least 

 below the apex. There is another division of epiphytes, 

 however which rose from the rocks, on hill and mountain, 

 and these have developed on different lines. When 

 growing from crevices it is easy to understand that a 

 soft juicy bulb like that of a Catasetum would be liable 

 to injury, and that a clump of roots could hardly find 

 room to spread. Something had to be done to over- 

 come these disabilities, and it was most beautifully accom- 

 plished. When we look at a Cattleya the whole contri- 

 vance is plain. The pseudo-bulb has been mounted on 



