Organography of plants, especially of the archegoniatae and spermaphyta . mongst the Droseraceae—the leaves are quite like those of Drosophyllum,but possess a very marked intercalary growth, and in correspondence there-with have no circinate ptyxis ^ The ptyxis of the leaves depends in myview partly upon the distribution of the growth in the leaf-development,and partly upon the amount of space available in the bud. A superficialexamination of some leaves whichhave laterally involute ptyxis showsthat they are always leaves which re-tain for a long time embryonal tissueand grow at the margin—mut
Organography of plants, especially of the archegoniatae and spermaphyta . mongst the Droseraceae—the leaves are quite like those of Drosophyllum,but possess a very marked intercalary growth, and in correspondence there-with have no circinate ptyxis ^ The ptyxis of the leaves depends in myview partly upon the distribution of the growth in the leaf-development,and partly upon the amount of space available in the bud. A superficialexamination of some leaves whichhave laterally involute ptyxis showsthat they are always leaves which re-tain for a long time embryonal tissueand grow at the margin—mutatismutandis—we have here the samerelationships as are found in leaveswhich are involute at the apex. Butthe influence of space-relationshipsappears in this, that a leaf in whoseaxil at a very early period a budarises is hindered by the bud fromassuming the ptyxis which it wouldotherwise do by its growth. Theordinary foliage-leaves of Calthapalustris, for example^ are in thebud laterally involute ; those, how-ever, which subtend a flower-budare spread out flat ^.. Fig. 202. Drosoph3llum lasitanicum. Leaf showingcircinate ptyxis. The tentacular glands are laid downin serial succession, but later ones are also {b) The Inception of the Leaf-Surface in Spermopiivta. In what we have said above we have dealt with the distribution ofgrowth in the primordium of the leaf in general. We must now brieflydeal with the laying down of the leaf-surface. The process relativelysimple where the leaf is from the laid down as a flat structure whichattains its mature configuration by a uniform stretching of the embr\-onaltissue in the transverse direction. Where, however, at a very early perioda portion thickens into a midrib, and is thus separated from a thinner partwhich is devoted to the making of the lamina, most complex relationshipsensue between embryonal growth and stretching. The types which havebeen created around which to group the forms that arc e
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