190 TRANSACTIONS OF THE [Sess. lxxvii. 



this growth-form of water-guards — that is to say, they are 

 not immediately shed, but wither on the stems and then 

 form a screen against the nitration of drying winds, as 

 well as the penetration of intense sun rays, and also hold 

 moisture as an asset, opposing to it as an agent of decay 

 their crustaceous desiccation and resino-glandular secretion. 

 Passim I may remark this desiccation of leaves in such 

 perennating undershrubs is a field of investigation as 

 yet unexplored — although it is one for which abundant 

 material is ready to hand in the cushion saxifrages of the 

 Dactyloid section. There are several types. In general 

 terms the extremes are what we may call the crisp and 

 the sodden. In the former the vestiges of the leaves, 

 representing often only the petiole or the vagina, become 

 brittle and crumple at once on handling, wound sur- 

 faces are not covered by cork, but by the hardening 

 of tissues; in the latter the vestiges soften and collapse, 

 and the ultimate clearance depends upon rotting of 

 tissues which never harden. All such changes are 

 correlated with secretion whether in the leaves or on 

 the stem, and the story of the attunement of the 

 several grades of these degenerations with a purpose 

 is there for the telling by any investigator who will 

 accept the suggestion. 



This undershrub habit is only developed in two other 

 species of Primula — apart from the European Auriculas — 

 so far as we know them at present : in the Californian 

 P. sufrutescens, A. Gray, and the Chinese P. dnjadifolia, 

 Franchet ; but the immediate ancestry of the former is not 

 that of this Chinese, Tibetan, and Baluchistan series, and it 

 itself tells of an adaptation to other conditions than those 

 which have brought about the evolution of the type of 

 which I am speaking ; and the latter is an interesting 

 parallel development on another phyletic line within the 

 Chinese area. 



The fragrance of the plants I am referring to is one of 

 their delightful possessions. On a warm day P. Forrestii, 

 Balf. fil., scents the atmosphere, and rubbing the leaves at 

 any time gives evidence of the perfume. Portions of dried 

 specimens if boiled will scent a room. The hair glands 

 are doubtless responsible for the odour in several species, 



