March 2, 1922] 



NA TURE 



27, 



aft( 



i 



Fig. I shows a group of dry sporophores on their 

 original matrix, bark of Populus sp., four months 

 after collection, and Fig. 2 a similar group of the 

 me gathering after revival. 



It has been remarked, but not further emphasised 



Prof. Buller {loc. cit.), that the pileus of 5. com- 



ne is of an absorbent nature. Indeed, the pileus 



LOWS a remarkable avidity for water, and the hairs 



imposing the woolly covering of the pileus enable it 



assured by the imbricate habit of S. commune. The 

 pileus of a plant growing at the top of a group of 

 sporophores collects all the raindrops that reach it 

 until it becomes saturated, after which the surplus 

 drips on to the pileus of a plant below, and so on, 

 until a whole group has obtained its full requirements 

 without the loss of a single drop. 



The moisture-content of the fully expanded fungus 

 and of the xerotropic form respectively are given 

 below. They are the results of one de- 

 termination only in each case. The 

 specimens were dried in a water-oven at 

 99°- 1 00° C. for five hours with all the 

 precautions usually taken in the estimation 

 of moisture. 



Normal sporophore 

 Xerotropic form 



water = 84* 3 per cent. 

 water=i6-o per cent. 



— Xerotropic form of Schizophylliim commune. N' uural size. 



I am indebted to Messrs. Murphy and 

 Son, Ltd., for the use of the accompanying 

 photographs, and to Mr. W. N. Cheesman, 

 of Selby, for the specimens, which were 

 collected at the Worcester foray of the 

 British Mycological Society in September 

 last. F. A. Mason. 



Bureau of Bio-Technology, Leeds. 



to absorb moisture with a greater rapidity than is 

 usual in fungi, so far as I am aware. 



The moist condition of the edge of the pileus 

 remote from the matrix, immediately after wetting 

 the latter, and rendered evident by the transition from 

 snow-white to a silvery-grey colour, led to several 

 experiments. It was found that the application of a 

 drop of water to one edge of a dry pileus resulted in 

 an immediate, and apparently uniform, diffusion of 

 moisture throughout the woolly covering of the whole 

 pileus — about 1-5 cm. diameter. The rate of absorp- 

 tion is much greater than that seen in the absorption 



-Schizophyllum 



Natural size. 



of ink by blotting-paper, and this fact was more con- 

 ^ incingly demonstrated by the use of a dilute aqueous 

 ilution of methylene-blue. 



It seems reasonable to suppose that the possession 

 of this property will enable the fungus, in its xero- 

 tropic condition, to take the fullest advantage of any 

 raindrop that may fall upon it by instantly absorbing 

 it. This supposition was tested by allowing drops 

 similar in size to tropical raindrops to fall from a 

 height on to the pileus, and it was observed that each 

 drop was immediately absorbed, without splash, until 

 saturation point was reached. Were its absorbent 

 power less, much water would be lost to the fungus 

 on account of its sharply convex outline. 



Conservation of water, in the case of a group, is 



NO. 2731, VOL. 109] 



Statistical Studies of Evolution. 



I SHOULD hke to suggest that the curves shown by 

 Dr. Willis and Mr. Udny Yule in their article in 

 Nature of February 9, p. 177, are capable of a 

 different interpretation from that which the authors 

 place upon them. 



It is possible that the curves are not, so to speak. 

 J. function of the organisms themselves, but rather of 

 their environment. 



Consider a habitable area of large size such as a 

 continent. The environment will vary in character 

 in different parts of the continent, the variation being 

 due to the presence or absence of environmental 

 limitations such as warmtn, moisture, particular food, 

 etc. 



In the continent considered, the greater the number 

 of environmental limitations in any area the greater 

 will be the number of possible combinations of these 

 limitations. Thus there will be in the continent a 

 great many different kinds of environment with a 

 large number of limitations (such as mountain peaks, 

 deserts, salt marshes, etc.), far fewer kinds of environ- 

 ment with a moderate number of limitations, and 

 still fewer with a small number of limitations. 



Since the continent we are considering is large, we 

 can consider it to be divided evenly between areas 

 with many Umitations down to areas with few Umita- 

 tions. But we have already seen that there are many 

 kinds of environment possible in areas with many 

 limitations, and therefore each of these areas with 

 one particular environment will be of small size. 



Conversely, the areas with fewer possible kinds of 

 environment and few limitations will be large in 

 size. 



In fact, could we plot the number of kinds of 

 environment possible in any one size of area against 

 size of area, we should obtain the same type of hollow 

 curve as that obtained by Dr. WilUs. 



Assuming, as is legitimate, that, on the whole, 

 organisms are adapted to their environments, it 

 follows that areas with many Umitations will require 

 many adaptations in the constitution of the organism, 

 and therefore few organisms will Uve in these areas, 

 and these will be highly adapted types or species. 



Hence the small areas with many Umitations will 

 each possess a few characteristic species ; and since 



L 2 



