THE ORCHID REVIEW. 



greenhouse or vinery. No other species can be grown with such ease and 

 certainty under ordinary conditions, in fact it can be potted like any 

 ■ordinary greenhouse plant, and is beautiful when in flower and graceful at 

 all other seasons. It has many beautiful varieties, and these, with some of 

 its hybrids, should not be lost sight of in this praiseworthy attempt to 



illustrate this article. __,^^__ 



EPIPHYTES. 



Notes of a lecture given at a meeting 

 on January 20th 



(Continued from page 104.) 

 The relation of these plants- to their nutrient substratum is a very 

 interesting question, because it enables us to see the particular way in 

 which they obtain their food. Those that grow on the bark of trees—and 

 they are numerous among Orchids— have a peculiar method of maintaining 

 themselves. Their roots are adnate to the bark, exposed on one side to the 

 .air, and form projecting lines and ridges, ramifying in all directions, and 

 often constituting a regular trellis-work cemented to the bark. These serve 

 as instruments of attachment, but at the same time they also absorb nutri- 

 ment from the substratum, the decaying bark upon which the plant is 

 epiphytic. During periods of drought this absorption is suspended, and the 

 plant is practically dormant, but when the rainy season commences there is 

 a long duration of wet weather, the water trickling over the surface from 

 the collecting ground of leaves and twigs overhead, descending lower and 

 lower, and bringing down not only tiny loosened particles of bark and 

 decaying vegetation, but mineral and organic dust which has collected, 

 dissolving all the soluble matter it finds on its way, and so reaches the 

 roots and rhizoids in the form of a solution of mineral and organic com- 

 pounds, chiefly the latter. In this way the requisite nourishment is con- 

 veyed to these curious epiphytes, whose period of active growth occurs 

 •during the rainy season. 



The roots of epiphytal Orchids differ from those of terrestrial plants in 

 being covered with a white papery substance, called the velamen, and the 

 cells of the velamen serve the double purpose of condensing or absorbing 

 aqueous vapour from the atmosphere, when any is present, and of protect- 

 ing the underlying cells from excessive evaporation during periods o - 

 •drought. In its absorptive character it is analagous with the outer cells of 

 the bog-mosses (sphagnum) and Leucobryum, where the small chlorophyll- 

 bearing cells are covered by large colourless cells, having very thin walls, 

 which are variously perforated, and not only absorb water in the liquid 



