444 SUMMARY OF CURRENT RESEARCHES RELATING TO 



abound near San Ramon in the Philippine island of Mindanao. The 

 combination of so homogeneous a group of plants abounding within so 

 limited an area, has afforded him a rare opportunity of studying the 

 effect of local differences of environment, of interpreting special adapta- 

 tions and peculiarities of form and structure, and of elucidating genetic 

 affinities. Among the more common phenomena studied were length of 

 stipes, its articulation, presence or absence of indusia, permanence of root- 

 hairs, ciliate or serrate margins. Concurrent evidence on these points 

 was available in two or more genera. The subjects treated of are dis- 

 cussed in the following chapters : — (1) The origin and geographical 

 affinity of the San Ramon fern flora ; (2) Local physiography and 

 classification by environment ; (8) Adaptations to common environment 

 and to special conditions ; (-4) Systematic application of the results. 

 The fern flora is shown to be entirely Malayan in origin. The vegeta- 

 tion is roughly classified under the heads : strand, salt marsh, savannah- 

 wood, high forest, rain forest, mossy forest ; and the species proper to 

 these habitats are classified in analytical tables showing the thickness of 

 frond and of upper and lower epidermal wall, the presence or absence of 

 chlorophyll in the epidermis, and of a chlorophyll-less hypodermis, the 

 number of stomata per square millimetre, and the average length and 

 width of a stoma. Explanations of these tables are given and liberal 

 comments and deductions added. The rain forest has been so shghtly 

 explored that the total of its species falls short of that of the high forest. 

 In the chapter on structural adaptations the main points considered are 

 (1) the vegetative frond (its size and marginal reinforcements, various 

 adaptations for rapid removal of water from the frond and for keeping 

 the nether surface dry, modifications of epidermis and stomata, nature of 

 the assimilating tissue, hydathodes, venation, articulate stipes) ; (2) the 

 rhizome (its modifications, correlations between length of rhizome and 

 length of stipes, shape or curvature of fronds and pinnfe to catch the 

 maximum of light, etc.) ; (3) root modifications ; (4) humus collectors, 

 e.g. Thayeria and some eight other species ; (5) myrmecophily, e.g, 

 Leca7iopteris and Polypodium sinuosum (the main service rendered by 

 the ants is a supply of mineral and perhaps organic food in their excreta 

 to plants which from their epiphytic and water-shedding habits have a 

 difficulty in securing a supply of mineral food) ; (G) reproductive struc- 

 tures (various adap'tations, the principles underlying which are, a, the 

 protection of the growing sporangium from injury by desiccation, etc. ; 

 h, the adequate desiccation of the mature spores to insure easy dis- 

 persal : c, the saving of the frond from injury by desiccation when the 

 spores are mature, the vast majority of Philippine ferns having persistent 

 and not annual fronds). In his fourth and last chapter the author dis- 

 cusses the local fern flora from the systematic side, pointing out some 

 characters observed in groups which are well represented locally, and 

 suggesting the probable genetic affinities of these ferns, a diagrammatic 

 summary of which is exhibited in the genealogical tree given on 

 plate iv. Plates i.-iii. contain ;37 figures representing structural 

 details. 



Vascular System of Ferns.* — A. G. Tansley publishes some 

 lectures on the evolution of the Fihcinean vascular system, part of a 

 * New Phytologist, vi. (1907) pp. 25-35, 53-68 (figs.). 



