212 MORPHOLOGY OF ANGIOSPERMS 



recently received more deserved attention from morpholbgists, 

 and which still so greatly needs investigation. 



I. Casuarinales.* — This includes the single family Casu- 

 arinaceae, containing about 25 species. Engler regard- the al- 

 liance as the most primitive because the ovule develops numer- 

 ous megaspores. This particular character can not be regarded 

 as distinctive, since among the Fagales the same character, 

 associated also with chalazogamy, occurs, and numerous mega- 

 spores are found among the liana les, Rosales, etc. The low 

 position, however, is justified by the primitive flowers, which 

 are either naked or with a bract-like perianth. 



The next two alliances are regarded as relatively primitive 

 on account of their naked flowers, together with the Casuari- 

 nales being the only naked alliances. 



II. Pipekales. — This includes the Saururaceae, Pipera- 

 ceae, Chloranthaceae, and Lacistemaceae, together containing 

 about 1,150 species, of which about 1,100 belong to the Pipera- 

 eeae. The results of the investigation of Peperomia pellucida 

 by Campbell and by Johnson indicate that the tropical Pipera- 

 ceae are probably most promising forms for morphological 

 investigation, and are to be considered in any discussion as to 

 the most primitive Dicotyledons. 



III. Salicales. — This includes the single family Salica- 

 ceae, containing about 180 species. 



IV. Myricales. — This includes the single family Myrica- 

 ceae, containing 10 species. The advance in floral structure is 

 shown by the fact that the several bracts near the flower may 

 be regarded as an extremely primitive perianth. 



V. Balaxopsidales. — This includes the single family Ba- 

 lanopsidaceae, containing 7 species. This is an uncertain type, 

 and raises the question of reduction. The staminate flowers 

 have a rudimentary perianth and an indefinite number of sta- 

 mens ; and the carpellate flowers have a bracteate perianth. 

 Engler calls attention, however, to the fact that there are no 

 intermediate forms for a reduction series, and that the indefi- 

 nite number of stamens is a primitive character. 



VI. Leitneriales. — This includes the single family Leit- 

 neriaceae, containing 2 species. The primitive character' of this 



* Vi:RTiriLLATAE of Engler. 



