626 SUMMARY OF CURRENT RESEARCHES RELATING TO 



thyllose formations. The adjacent assimilatory tissue has a poorly 

 developed intercellular system. The pneumatodes are to be regarded as 

 a characteristic and specialized form of epidermal tissue for supplementing 

 the work of the stomata. 



Diaphragms of Air-cavities in Plants.* — Le Blanc has studied the 

 mechanical tissues of Sagittaria, Potamogeton, and other aquatic plants, 

 and finds that they possess numerous diaphragms, especially in those 

 organs which are exposed to the movements of the water. These struc- 

 tures appear to support the greatly reduced vascular system, and are 

 composed of minute cells with curious cavities scattered between them 

 at frequent intervals. They often contain starch and other reserve 

 materials, also chlorophyll, oil, resin, salts of lime, etc. ; they facilitate 

 the passage of gases throughout the plant. Similar diaphragms are 

 found in many aerial plants, especially in the Monocotyledons, and cannot 

 be regarded as a special adaptation to aquatic conditions. They are 

 formed under the influence of a strain producing a partial separation of 

 the cell-membranes, and alternate swelling and contraction of the cell- 

 contents. 



Anatomy of the Asclepiadese.f — Gr. Puech has studied the anatomy 

 of several species of Asclepiadese from Madagascar, and the present 

 paper concludes with a new system of classification based upon the 

 anatomical structure. The species examined belong to the following 

 genera : — Decanema, Sarcostemma, Drepanosteyna, Cynanchum, Folotsia, 

 Mahafalia, and Prosopostelma. The anatomical characters upon which 

 classification is based include the structure of the pericycle, the lati- 

 ciferous vessels of the stem, cellulose fibres in the bark and cortex, etc. 

 Some interesting facts are l»rought out, e.g., the genus Cynanchum 

 comprises two distinct groups of species, in one of which cellulose fibres 

 are present in both bark and cortex, while in the other group no such 

 fibres exist, and the cortex is entirely parenchymatous ; thus, one 

 group represented by G. macranthum is closely related to Sarcostemma 

 and Drepanostema, while the other group, represented by C. impUcatum, 

 is shown to be related to Folotsia. In spite of such conclusions as this, 

 it is proved that a remarkable homogeneity of anatomical structures is 

 found in all the species, a feature that appears to be the result of simi- 

 larity of environment. 



Syncotyly and Monocotyly among Dicotyledons. | — A. Guillaumin 

 contributes a few remarks upon the monocotyledonous condition of 

 certain seedlings of Dicotyledons. The writer regards this, on anatomi- 

 cal grounds, as the result of fusion of two cotyledons, or suppression of 

 one of them. Syncotyly may arise where two normal cotyledons are 

 present, or where there is one normal and one supplementary cotyledon ; 

 in the former case the two cotyledons may fuse at one side only or on 

 both sides. These facts seem to show that syncotyly and monocotyly 

 are insecure grounds upon which to base a phylogenetic relationship. 



* Rev. G6n. Bot., xxiv. (1912) pp. 233-43 (1 pL). 

 t Rev. Gen. Bot., xxiv. (1912) pp. 329-43. 

 X Rev. G6n. Bot., xxiv. (1912) pp. 225-32. 



