552 



BOTANY 



PART II 



the result of branching during the development of the leaf. The 

 margin of the leaf presents considerable variety. The venation is as 

 a rule reticulate (Fig. 556). 



The flowers of Dicotyledons exhibit a wide range in their appear- 

 ance and construction. Most frequently they can be derived from a 

 type with five whorls of five members ; increase and decrease of the 

 number both of the whorls and the members are met with. The 

 Dicotyledons are divided into the two series of the Choripetalae (with 



free perianth segments) and the Sym- 

 petalae (with the petals coherent). 



The classification adopted here corre- 

 sponds in the main to that in ENGLER and 

 PSABTL's Nat&rliehen Pflanzen-familiei>,\>ul 

 the grouping together of a number of families 

 under the older ordinal names has been 

 retained. 



A number of questions raised by HALLIEK 

 in his recent work on the natural (phylo- 

 genetic) system of classification of flowering 

 plants deserve consideration. For instance 

 the separation of Choripetalae and Sym- 

 petalac, which HALLIER abandons, is doubt- 

 less artificial and not altogether satisfactory. 

 The recognition of the catkin-bearing forms 

 as reduced and the derivation of the Dico- 

 tyledons from forms like the Magnoliaceae 

 has much in its favour. The derivation 

 of the Monocotyledons from the Polycarpicae 

 is supported on <piite different grounds by 

 E. SARGAKT. While systematic Botany 

 must endeavour to attain new points of view 

 and never to regard the prevailing classi- 

 fication as a sort of noli me tangere, 

 further developmental studies are necessary before a thorough revision of the 

 present system can be contemplated. An investigation by STRASBURGER into the 

 ovule and the formation of the endosperm in Drimys Winteri, a plant which in 

 the structure of its wood recalls the Gymnosperms, has yielded no indication that 

 the gap existing between Gymnosperms and Angiosperms can be bridged by the 

 study of existing forms. 



Fi<;. 656. Leaf of CVwtalipiM with reticulate, 

 venation. (} nat. size.) 



Series I. Choripetalae ( 15 ) 



Order 1. Piperinae 



The single Family of the Piperaceae contains a few tropical genera. 

 Flowers as a rule unisexual and without perianth, associated in spikes ; 

 typically trimerous but usually reduced. Ovary unilocular, ovule 

 solitary, basal and atropous. Fruit drupe -like. The embryo is 



