190 Uetrospective Criticism, 



fieldSj'and principally on a gravelly soil. i7ypdricum pAlchrum I have always considered as a 

 tolerably common plant, but it is marked with a star. Among those plants collected in Herts, the 

 Asperula odorata and Afenyiinthes trifoliata certainly deserve no place. The alpine plant, the 

 Biirtsia alplna, from its having been found in Epping Forest, only shows that plants may be found 

 within a few miles of London, which botanists have never thought of collecting so far from their 

 usual places of growth. Thus the Stratibtes aloides fills a pond on Wandsworth Common ; the 

 Tofi&ldM! paKistris has been found, I believe, by the foreman (Mr. Bevis?) of the garden at Syon 

 House, on Wimbledon Common, with other rarities. I found the Erythra^a pulch(:;lla S^nith in a 

 boggy part of a common that runs by the side of the road leading from Kingston to Leatherhead ; 

 and, what is more singular, on a strong clay soil, as this plant is usually found by the sea-side, and 

 consequently on a sandy soil. In the next page, I find that the Ixodia procumbens is mentioned 

 by Mr. Daniel Stock as a plant new to him and to the botanists there. I should conceive that there 

 is no good-sized common or heath where this plant may not be found. If this plant had been rare 

 in Suffolk, Sir J. Smith would have mentioned it in his English Flora. — T. M. Oct. 1. 1829. 



Plants with lohite Flowers. — Various lists of varieties of plants with white flowers have been 

 given in your valuable Magazine, and much interest (if we may judge from the numerous corre- 

 spondents who have appeared) seems to be taken on the subject ; but, after all, very little has been 

 brought to bear upon the point, as your correspondents have mostly given bare lists, without 

 stating the nature or quality of the soil, or peculiar habitat of their plants : so that, from the mere 

 enumeration of varieties of plants, without reference to the circumstances I have mentioned, we 

 gain little advantage, and no conclusion can be drawn. Having myself frequently met with varie- 

 ties of plants in botanical rambles, I have tried to ascertain what causes operate to change the 

 colour of the blossom, and I find that it is sometimes merely the effect of a peculiar habitat ; some- 

 times the nature of the soil on which the plant grows appears to be the only reason ; and occa- 

 sionally an accidental circumstance has given a richness to the soil, and manuring it has caused 

 an alteration in the appearance of its vegetation : e.g. the common bird's-foot trefoil (L6tus cor- 

 niculktus), which in dry upland pastures is of a brilliant yellow, on the red marly banks of the 

 Severn assumes a deep sanguine orange hue ; and a friend informs me that he has observed it on 

 the lias marl, a few miles on the western side of Worcester, perfectly white : in this case the soil 

 affects the flowers of the plant. The bluebell (SclUa nutans) is not uncommon, in the vicinity of 

 Worcester, with white blossoms ; but I have uniformly observed, wherever it so occurs, that the 

 spot is uncommonly shady, or that a wood has, at no very distant time, occupied the place. In these 

 cases, the peculiar locality has an effect upon the plant; and in a deep shady wood on the western 

 side of the Malvern Hills, where, this summer, I found a number of luxuriant plants of the Paris 

 quadrifblia, in one spot of the thicket where a straggling sunbeam was admitted through the trees, 

 and glanced upon one of the plants, the blossom was withered and shrunk, and the four leaves 

 variegated. In illustration of the accidental luxuriance of plants, I may mention that I found the 

 O'rchis mbrio, in a moist field near Worcester, double its usual height, and with flowers of a deli- 

 cate light pink ; and around the plant, at this particular spot in the marsh, I noticed some swine's 

 dung had been dropped. In the list of plants (p. 161.) I have noticed in this neighbourhood, vary, 

 ing in the colour of their flowers, though I have mentioned the particulars above, yet, in many 

 instances, I cannot satisfactorily account for the variation. I think, however, the nature of the 

 soil should always be examined and noted; and I would suggest to your correspondents to observe 

 this in their botanical communications. — Edwin Lees. Sept. 17. 1829. 



Gry'phcB'a arciidta. — I wish your F.R. S. had not sent you his drawing of 

 two of the most common fossil shells in England, the Gryphae'a arcuata. 

 (fig. 20. p. 95.) Their position must be accidental, for they have lids like 

 oysters ; indeed Linnaeus classes them with oysters. — R. B. Jan. 4. 1830. 



Cucullus simplex. — Sir, At p. 95. of your Magazine, you have favoured us with a drawing of 

 two fossil shells, which, your correspondent says, " appear to be the Cucullus simplex of Rumphius 

 (tab. 59. tit. B.)." I think, if he refers to Sowerby's Recent and Fossil Conchology, he will find the 

 said fossils to be Gryphites ; and, according to Lamarck, very distinct from CucuUse^a. I am, Sir, 

 &c. — A Subscriber. Jan. 1. 1830. 



Meteorological Observations. — Sir, I feel obliged by Mr. Tatem's notice ([). !55.) of my remarks 

 on his meteorological observations; and, in compliance with his wish, I shall, with much plea- 

 sure, explain the course adopted by me in making out my register. I have already briefly alluded 

 to this at p. 204. Vol. II. ; but perhaps I have not been sufficiently explicit. In the article Me- 

 teorology, p. 159. of Brewster's Encyclopcedia, it is assumed that the mean temperature, by daily 

 observations at 10 a. m. and 10 p. m. with an ordinary thermometer, coincides with the mean of 

 the dnUy extremes ; and the mean taken in this manner, compared with the mean of the daily 

 extremes for 71 months, gives only a difference of 0*3O, and in some years there is not the smallest 

 fractional difference ; and my own observations corroborate what is there stated. For example : 

 at 10 A. M. I find the thermometer indicate 50°, and at 10 p. m. 40°. These results are marked in 

 separate columns, and the mean 45° extended in a column by itself. On examining my night and 

 day thermometer at 10 p.m., I find the minimum 38°, and the maximum 52° ; the mean of which 

 is also 45°. Should any fractional difference occur, the mean of means is taken for the true 

 mean ; but knowing that such difference is extremely slight, I have repeatedly recommended 

 taking the mean, as stated above, with an ordinary thermometer, with a view to encourage gar- 

 deners to keep registers, who may not have self-registering thermometers. Every ten days the 

 true mean is added, and divided by 20 for the mean of that decade. The monthly mean is obtained 

 by dividing the sum of the true daily means by the number of days in the month, and the annual 

 mean by dividing the sum of these by 12. The mean of the barometrical range is taken in the 

 same manner. The dew point is ascertained at 2 o'clock by plunging a thermometer in a glass of 

 water, cooled, if necessary, by frigorific mixtures, noting the temperature when the dew ceases to 

 appear on the outside Of the glass. Spring water at 47° often effects this in summer without any 

 mixture. I also employ Leslie's differential thermometer for a check, but the calculations are 

 tedious. 



The annual average temperature at this place for the last seven years I find to be 477° ; and at 

 Wycombe, according to Mr. Tatem, it appears to be 46-430. (Vol. II. p. 96.) Annat Gardens, where 

 my register is kept, are 4-460 farther north than Wycombe ; and, according to a formula given by 

 Mayer [Brewster's Encyc , p. 156., art. Meteorology), which, in many instances, I have found to 

 ap'.iroximate nearly to the truth, the annual mean temperature here should be 47'5o, which is 

 within Q-1° of the seven past seasons. According to the same authority, the annual mean tcm- 



