Feb. 25, 1886] 



NA TURE 



389 



that are immensely complicated. Those of the former 

 are generally of the more simple kind, but in the aroids 

 and Smilax they equal in complexity, and resemble, 

 dicotyledons. It is not among these, however, but, as in 

 zoology, among the embryonic stages, that the ancestral 

 forms are likely to be traced. In many young plants the 

 first leaves are very different in form and structure to 

 those born when maturity is reached. Examples are 

 given of sheathing, amplexicaul phyllodes in Cicer aris- 

 tinium, Querciis piibcscens. Asparagus officinalis, and 

 some Rosacea, most of which are scale-like and parallel- 

 veined. In Aralia nymphciTfolia the stipules embracing 

 the young shoot are of considerable size and adherent for 

 some time. They have a fine parallel venation which 

 scarcely anastomoses and resembles not only the fully- 

 developed leaves of some monocotyledons, but the petals 

 and sepals of many flowers. In A. Sieboldi the bracts 

 enveloping the buds and young shoots are similarly con- 

 structed, the petiole and true leaf barely emerging from 

 their summit. The sheath, representing the primitive 

 leaf, is in some Umbellifera:, as the fennel, more im- 

 portant than the secondary leaves, and in one dicotyle- 

 don at least, Eryngium bromeliafolium, the latter are not 

 developed at all, the leaves resembling those of a yucca. 

 On the other hand, it is not every monocotyledon that 

 has preserved its primitive leaves only. In CcDina indica, 

 for example, the inferior and sheathing portion represents 

 the primitive leaf, the middle part, or petiole, the original 

 mucronate apex, and the blade the secondary leaf. 

 Nearer the flower-spike only the primitive leaf-develop- 

 ment remains in the form of bracts. The same characters 

 are observed in Strelitsia rcgina. In Aroideae the first 

 leaves are simple and sheathing and the second as com- 

 plex as those of dicotyledons. Smilax furnishes an 

 example of a monocotyledon which has elaborated pre- 

 cisely the same kind of secondary leaf as a dicotyledon. 

 In the grasses the primitive leaf appears on the under- 

 ground rhizome as a sheath, later reduced to the ligule, 

 while the ribbon-leaf is the homologue of the ordinary 

 dicotyledonous leaf. In palms the primitive leaves are 

 traceable in germination and later in the spathes and 

 bracts, and in an altered condition in the leaf petiole, 

 only the fan part being the secondary leaf. 



The ancestral " pro-angiosperms " are supposed to have 

 borne leaves such as are found diminished or masked in 

 so many of their existing descendants — that is, entire, 

 more or less elongated, ribbon-like leaves, amplexicaul at 

 the base, attenuated and mucronate at the apex, and tra- 

 versed by numerous longitudinal veins, connected by 

 transverse veinlets, or even areolated. 



Monocotyledons have, as a class, preserved their primi- 

 tive foliary appendages more perfectly than dicotyledons, 

 in which they are frequently so reduced as to be barely 

 traceable as lateral expansions of the petiole, or in minute 

 stipules. 



The flower is an organ common to both, and must, 

 therefore, have been produced before the two classes had 

 become differentiated. The relative simplicity of struc- 

 ture seen in their several parts is thus explicable— sepals, 

 petals, and bracts being frequently almost reproductions, 

 as to form and venation, of the vagina, or the first sheath 

 leaves, which in many plants succeed the cotyledons, and 

 the terminal mucro can also sometimes be detected. 



Examples of primitive flowers are seen in Maguoliaccce, 

 Raininciilaceiv. and Nymphacccc, but others have doubt- 

 lessly been profoundly modified to meet the needs of 

 fertilisation. That the sexual leaves bearing the micro- 

 and macro-sporangia — stamens and pistils — are similarly 

 modified leaves, is also apparent in the case of Magnolia. 

 Originally the " pro-angiospermic " flower must have con- 

 sisted of an axis bearing the sexual appendages spirally 

 disposed one above another, the microsporangial leaves 

 at the base, and the ovule-bearing ones above. Though 

 the flower has became consolidated through the shorten- 

 ing of the axis, its primitive spiral arrangement is trace- 

 able in a multitude of angiosperms. 



Even the stems in the two classes are not really funda- 

 mentally different, the permanent presence or the absence 

 of a productive region of cambium alone sufficing to have 

 originated the two divergent types. In the remote past, 

 before even the seasons were well defined, the cambium 

 layer may have existed in an irregular or fugitive manner 

 in the " pro-angiospermic," as it did in the " pro-gymno- 

 spermic" stem, and thence increasing differentiation have 

 produced the two parallel series forming respectively 

 at last dicotyledonous and monocotyledonous stems. 

 Branching probably took place in such primordial stems 

 by means of solitary terminal buds, accompanied perhaps 

 by a restricted number of lateral ones, after the fashion 

 of the screw-pines, aroids, and aloes. 



Such was the nature of plants in their " pro-angiosper- 

 mic "stage. Even the initial difference in the number 

 of cotyledons characterising each class is explicable by 

 supposing them to have been originally of unequal size, 

 and that progressive differentiation led, in the one direc- 

 tion to equalisation, and in the other to suppression. 

 The inequality is preserved in Nymphaccce, which thus 

 serve to diminish the difference in this respect between 

 the two classes. J. .Starkie Gardner 



OUR BOOK SHELF 

 A Tangled Talc. By Lewis Carroll. With Six Illus- 

 trations by Arthur B. Frost. Pp. 153. (London : 

 Macmillan and Co., 1885.) 



The first half of this delightful book consists of ten 

 chapters, or " knots," as they are labelled by the author. 

 Each of these contains a quaint and humorous descrip- 

 tion of some romantic episode, imagined in order to 

 furnish occasion for proposing certain ingenious mathe- 

 matical problems to the younger actors in the drama. 



The author states that his intention was to embody 

 these questions in each knot " like the medicine so dex- 

 terously, but ineffectually, concealed in the jam of our 

 early childhood." This, however, may be noted : in the 

 several doses presented in the volume before us the 

 patient may assimilate all the jam, and, at will, reject the 

 medicine. 



The fun and humour with which these sketches sparkle 

 may be enjoyed — and the many sly hits to be found 

 therein may be appreciated — by those who are unwilling 

 or unable to grasp the mathematical question involved. 



And for another class of readers there is furnished, in 

 an appendix which fills the latter half of the book, plenty 

 of strong medicine ready to be taken undiluted, if so they 

 choose. 



" A Tangled Tale " having originally appeared as a 

 serial in the Montlily Packet, many of the fair readers of 

 that magazine, and also some of their brothers, sent up 

 answers month by month to the questions proposed, and 



