146 NATURAL SCIENCE. March, 



Professor Marshall Ward on " Modern Botany." 

 In the first lecture of his course on " Some Aspects of Modern 

 Botany" (Royal Institution, February 13), Professor Marshall Ward 

 mentioned that mediaeval botany consisted in the collection of native 

 plants, and the attempted identification of these with medicinal and 

 economic plants, described by the ancients, or known from distant 

 countries. Difficulties in identification led to discovery of the fact 

 that different countries had different plants, and thus was laid the 

 foundation of the science of geographical distribution. The careful 

 study of large numbers of specimens led to the evolution of the idea 

 of natural affinities. Efforts at classification were at first vague ; men 

 had to learn what parts were comparable. For a time they were like 

 children, distinguishing an oak from a buttercup by the acorn and the 

 flower. Their belief in the existence of sharp lines, which could be 

 brought out if plants were repeatedly and elaborately described, 

 contrasted somewhat with the exaggerated importance which is 

 to-day ascribed to points of resemblance as opposed to points of 

 difference. 



Systematists have not yet reached the end of all things. The 

 broader divisions of plant classification may be settled ; it may be 

 possible for an expert to indicate, almost at a glance, the exact 

 position of a new species ; but the work will not be complete till 

 the list includes all existing and fossil species from all parts of 

 the world. Then the ultimate aim may be achieved, namely, 

 the construction of a genealogical tree showing the true affinities of 

 all known plants. The lecturer went on to emphasise the value of a 

 good Flora, instancing the " Flora of British India," "which, we are all 

 so glad to know, is now nearly complete." It is not merely a list of 

 the plants growing in a certain country, but it tells much about 

 character and localities, range in altitude and distribution in other 

 parts of the world. 



The remainder of the lecture was occupied by discussion of some 

 questions of variation and adaptation. First, Professor Ward remarked 

 as to the "purpose" of a hairy covering, of which the Alpine edelweiss 

 supplied an illustration. Consideration showed that this was a con- 

 comitant, not of cold, but of dry situations, and was one of several 

 means adopted by the plant for lessening the loss of water by transpi- 

 ration. The danger of using such adaptive characters for systematic 

 purposes was effectively illustrated by a slide showing a Mexican 

 Echidnopsis, a member of the Cactus family, and an African Euphorbia, 

 two fleshy-stemmed plants which could scarcely be distinguished 

 except by careful examination. The red colour often assumed by parts 

 of plants other than flowers, especially young leaves, afforded an 

 instance of the danger of pushing an explanation too far. In many 

 instances it doubtless served to absorb some of the sunlight and so 

 protect the chlorophyll of young organs, but such a case as the red 

 colour in the lower layers of the floating leaf of a water-lily demanded 



