1893. NOTES AND COMMENTS. 405 



The Ancestors of the Cat. 



The above-named authors in the same communication put forth 

 the hypothesis that the cats, instead of being directly related with 

 the other Carnivores of the present day, are independently descended 

 from the Creodont genus PalcBonidis. In view of the close similarity 

 between the Cats and the Civets (the latter being clearly related to the 

 Dogs), this is " parallehsm " with a vengeance. Does it never strike 

 the promoters of such extreme views that by proving (!) the want of 

 relationship between apparently closely allied animals they may be 

 cutting away the ground from beneath the foot of the evolutionist, 

 since, if resemblances are, so to speak, fortuitous, why should not we 

 revert to the doctrine of separate creations ? That parallelism does 

 exist in Nature, we are fully prepared to admit, but it is not omni- 

 present. However, when once the ball is set rolling in a certain 

 direction, everyone thinks it necessary to give it another push. 



Aerial Roots of Orchids. 



The velamen, or characteristic external covering of the aerial roots 

 of epiphytic orchids, forms the subject of a note by P. Groom in the 

 last issue of the Annals of Botany. As terrestrial orchids are almost 

 invariably devoid of a velamen, it is usually assumed that the aerial 

 orchids acquired theirs subsequently to the adoption of an epiphytic 

 mode of life, but it is suggested that the few exceptions may indicate 

 the existence of the covering in a previous terrestrial mode of life. 



With a view to getting some light on the date of origin of the 

 velamen, the author has made observations on Grammatophyllum 

 speciosiim and species of Broniheadia, both at Singapore. The former 

 is one of the few orchids which grow naturally both as terrestrial and 

 epiphytic plants, and can be found growing in the jungle when it has 

 happened to fall off a tree. When a terrestrial plant, the velamen is 

 not only retained but even strongly developed in the soil, while the 

 upwardly-growing aerial roots characteristic of the epiphytic habit, 

 which Schimper has shown to be respiratory organs, are still 

 developed. 



Broniheadia alticola lives in the full blaze of the sun on high tree 

 tops, and has a peculiar two-layered velamen, while in B. palustris, 

 which is terrestrial, the velamen is fundamentally similar, but lasts 

 only for a short time, peeling off and disintegrating. This points to 

 the conclusion that this covering is essentially adapted to epiphytic 

 plants, and was evolved subsequently to their assumption of an aerial 

 mode of life. 



The two sets of observations seem to give contradictory results. 

 In the first, the velamen being more highly developed in the sub- 

 terranean ; in the second, in the aerial roots ; but the explanation 

 is found in the fact that the function of the structure varies. In 

 Gravimatophyllum it is essentially an absorbent organ, which not only 



