146 



HARDWICKE'S SCIENCE-G;0 SS IP. 



frequently in an analogous manner. All agree that 

 during the first period they are so like each other, 

 that it is almost impossible to separate one from an- 

 other of the younger forms of the most dissimilar 

 species. There is no doubt whatever that they all 

 begin with a short stalk and an undivided lamina ; 

 that this stalk continues always short in some, and 

 lengthens very considerably in others ; and that the 

 lamina in some remains undivided, but in others is 

 lachiiate. But it is especially to be observed that 

 this lamina — whether it be undivided or herniate— 

 is variable in most species. Thus all are at first 

 small and extended in length, with a more or less 

 wedge-shaped base; but the wedge-shaped base 

 becomes heart-shaped, and even kidney-shaped in 

 some ; in others it retains its wedge-shaped form 

 throughout the whole state of development. It is 

 known that most, at least, of the species periodically 

 change their lamina ; and the new lamiua becomes 

 larger and broader than the old one. The young 

 lamina is thin, in colour rather inclining to green 

 than to light brown ; in different species the lamina 

 is at a later period thinner or thicker, and with a 

 different tint of colour. The fructification appears 

 in different species, not only in different parts of the 

 lamina, but the sori extend iu different directions, 

 although they do not seem to assume precise 

 forms." 



Suites of specimens of Alaria, at all periods of 

 growth, should be collected, and especially with 

 fructification, and the differences of form observed. 

 In some species the lamina is linear; in others 

 shorter and more oblong or oval; in others much 

 extended and strictly linear. There are differences, 

 also, in the relative breadth and length of the 

 lamina; some are wider than others in proportion 

 to their length; one, for instance, in the Sea of 

 Okhotsk is recorded as 50 feet in length and from 

 2 to 4 inches in breadth ; while a gigantic specimen 

 from Spitzbergen is 1 foot 6 inches broad and 6 feet 

 long. In some the base of the lamina is cuneate 

 and decurrent ; in others ovate ; in others, again, 

 cordate. The stem, which is short in young plants, 

 lengthens with age. It varies, however, in length, in 

 several species from 1 to 2 inches, in some to 4 feet, 

 and more in others, and is covered with the remains 

 of the pinnae of several years' growth. The pinna? 

 vary in form and size in different species. Dif- 

 ferences also occur in the thickness or thinness of 

 the lamina and likewise in the costa, which is more 

 elevated in some species than in others. Hence the 

 necessity of accurate observation and comparison 

 of many examples before the species can be deter- 

 mined. 



I must now refer to the mode of preservation. 

 Prof. Agardh states that the best way of preserving 

 algae is to salt them down in a cask or tub. First 

 put into the cask a layer of salt, then a layer of 

 algae, then salt, then algae, and so on, until the 



vessel is full. The algae should not be previously 

 washed in fresh water, as the salt assists in pre- 

 serving their suppleness. The algae brought home 

 by the Swedish Expedition from Greenland and 

 Spitzbergen in the year 1870, and which afterwards 

 formed the subject of Agardh's Essay, were pre- 

 served in this way ; and the Professor states that, 

 when opened, they were found to be almost as 

 fresh as when first taken out of the sea, and in an 

 admirable condition for examination. 



MANNA OE THE DESERT {Lecanora or Lichen 



esculent a, and L. affinis). 



FN the supplement to the new edition of the 

 ■*- " Treasury of Botany," under the head of 

 "Manna," it is stated that " Lecanora escuhnta and 

 L. affinis are called ' Manna ' in Armenia and Algeria, 

 and are eaten in times of scarcity " ; the writer 

 might have added, " a vegetable substance supposed 

 to be the manna on which the children of Israel 

 were fed." 



As some may not have read the articles on this 

 subject in Science-Gossip for March, 1872, p. 60, 

 and August, 1872, p. 186, and one on the same 

 subject by Lindley in his " Vegetable Kingdom," 

 it may be as well to draw attention to them, and 

 at the same time to add a few further remarks on 

 the subject. It is probable that there may have 

 been some hesitation by the writer in the Supple- 

 ment, in consequence of the conclusion arrived at 

 in the "Dictionary of the Bible," published by 

 Murray in 1863, viz., that because the shrubs pro- 

 ducing the common manna of the shops, and the 

 natural products of the Arabian deserts and other 

 Oriental regions, which bear the name of manna, 

 give a supply only three or four months in the year, 

 and have not the qualities ascribed to the manna of 

 Scripture, and for other reasons equally inappli- 

 cable, therefore the manna of Scripture was wholly 

 miraculous. It should be borne in mind, however, 

 that the lichen (or Lecanora esculenta and L. affinis) 

 may be gathered during the whole year, and, as 

 Lindley says, "appear suddenly in immense quan- 

 tities in Persia, Armenia, and Tartary, where they 

 are eagerly devoured by the natives, who fancy they 

 must fall from heaven, not knowing how else to 

 account for the prodigious numbers of these plants, 

 of the origin of which they are ignorant " ; adding, 

 " Parrot says that in some districts they cover the 

 ground to the depth of five or six inches." There 

 is no reason, therefore, to suppose that the manna, 

 though miraculously sent, was not a natural product, 

 any more than the water from the rock of Horeb, 

 or the quails, which, though natural themselves, 

 were miraculously sent. 

 The apparent difficulty arising from the fact that 



