208 SUMMAEY OF CUREENT RESEARCHES RELATING TO 



by never reachin,^ across the tracheides. These two features have been 

 regarded as specially characteristic of the •' bars " found in the Arau- 

 carineae, and have been used as an argument in favour of the Abietinean 

 ancestry of the latter. Not only does the present discovery render this 

 argument valueless, but a comparison of the "bars" in the different 

 regions of the Abietinese appears to favour a reverse relationship. The 

 type of "bar" found in the Cycads and Araucarians is without doubt 

 ancestral to that found in a more specialized form in the higher conifers, 

 and still persists in the primiti\(' parts, i.e. the cone-axis and root of 

 the latter. 



Reproductive. 



Pollen-formation in Monocotyledons.*— L. (iuignard contributes 

 a second note upon the method of pollen-formation in Monocotyledons. 

 The author has now examined three other genera belonging to the 

 Iridaceae, viz. Gladiolus, Tigruiia, and Crocus, and finds that they agree 

 with those previously examined in forming their pollen by simultaneous 

 quadripartition. It appears, therefore, that this mode of pollen-forma- 

 tion is general throughout the Tridacete, and that both this group and 

 that of the Orchidacete resemble the Dicotyledons rather than the 

 Monocotyledons in this respect. 



CRYPTOGAMS. 



Pteridophyta- 



(By A. Gepp, M.A. F.L.S.) 



Anatomy of Nephrolepis volubilis.f — Birbal Sahni gives an account 

 of the anatomy of Nephrolepis voluhilis, with remarks on the biology 

 and morphology of the genus. This fern is highly specialized. The 

 primary stolons climb some r)0 feet up forest trees, and enable lateral 

 plants, borne on them at intervals, to reach heights far above the 

 mother-plant which is rooted in the soil. Two to four shorter stolons, 

 wiry and irregularly coiled, appear on each lateral plant, and seem 

 to be contact-sensitive. They are climbing organs. The stolons 

 possess a single axial polyarch exarch protostele. In the endodermis 

 peculiar radial strut-like bodies were found. In the lateral plants 

 the basal protostele becomes soon modified into a primitive form of 

 dictyostele at the apex : the first leaf has a compound leaf -trace ; there 

 are no roots. The primary stolons of several species of Nephrolepis are 

 probably positively hydrotropic. In N. ramosa and N. altescandens, 

 two closely allied species without stolons but with scandent rhizomes, 

 the internode has a dictyostele of the very simplest type. In N. ramosa 

 the vascular structure at the base of the branch and leaf-traces is 

 almost identical, and recalls the condition of the Hymenophyllaceai. 

 In N. alfoscatidens the leaf-traee arises as two separate strands, in 



* Comptes Eendus, clxi. (1915) pp. 623-^5. 



t New Phytologist, xiv. (1915) pp. 251-74 (1 pi. and figs.). 



