PIIANEIIOGAMIA : FOLIAR ORGANS. 27o 



of the base of the leaf. The careful observation of the germination of a 

 leguminous plant with greatly developed stipules would suffice to esta- 

 blish this opinion without any application of more fundamental re- 

 searches into the course of development. For example, in Orobus aibus, 

 Lathyrus sphcericus, the first leaf after the cotyledon is a simply lanceolate 

 leaf passing immediately into a broadly winged petiole. The second leaf 

 is somewhat longer, yet still simple, and the two appendages adhering to 

 the sides of the petiole must be called stipules ; the third leaf is tripartite 

 (f. trifidum\ with stipules, the connection of which with the petiole still 

 appears very considerable ; lastly, the fourth leaf is a compound leaf 

 with two leaflets, a terminal point and stipules, the connection of which 

 with the long petiole is in proportions almost too slight to be noticed. 

 The condition is similar in Pisum sativum (Plate III. fig. 1.), and every- 

 where ; and from this alone it may be seen that petiolus alatus, stipules 

 adnatce, and stipulce liberce are one and the same part in different 

 degrees of development. The same gradual development occurs in most 

 buds ; and, for instance, in Prunus Padus the leaves of the bud run 

 through exactly the same series of forms from below upward as the 

 germinating Leguminosce. If this had been looked into, more than half 

 of that terminology would have been wholly superfluous, even for De- 

 scriptive Botany, if, as a general rule, all those processes which go off, 

 not merely from the borders, but at the same time from the surface, of 

 the leaf, were called ligula ; all distinct appendages of the border, petiolus 

 alatus (e. g. stipulce adnatce, lanceolat(e= petiolus alatus, alls lanceolatis)-, 

 finally, all parts which appear to be entirely free, stipulce (e. g. ochrea= 

 stipula vaginans), &c. In all these there are many further investi- 

 gations still to be made, since, when I can even say that I have minutely 

 traced the development in some fifty plants, this is far too few to carry 

 back the so various phenomena, with complete certainty, to their funda- 

 mental structure ; and there are still many families remaining in which 

 I have not hitherto had opportunity to examine any plant. A large 

 field for inquiry is especially left in the related parts of the floral leaves. 

 In Lychnis the course of development, in Narcissus both this and mon- 

 strosities (e.g. the double N. poeticus),show that this part exists as ligula; 

 wholly similar results may certainly be expected for the fornix of the 

 Boraginece, and other similar phenomena. Lastly, the nature of stipellce 

 has yet to be cleared up by the history of their course of development. 



V. Every leaf, as already observed, originates as a little conical 

 papilla at a definite point on the circumference of the axis. Even 

 the sheathing leaves are produced in this manner, and at the point 

 which corresponds to the middle line (the mid-nerve) of the future 

 leaf by degrees, and as it is pushed up further from the axis, the 

 parts of its circumference take part more and more in the develop- 

 ment, and thus the base of the leaf gradually becomes broader, until 

 it completely surrounds the axis. If the development of cells, or 

 the expansion of existing ones, continues on the borders of the base 

 of the leaf, beyond the degree required to surround the axis, the 

 newly-formed, still soft and almost gelatinous cells of the two 

 borders of the base of the leaf become applied upon one another, 

 and become united as firmly as the cells of a continuous tissue ; in 

 this way the lower part of a leaf then becomes a closed, undivided 



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