80 SUMMARY OF CURRENT RESEARCHES RELATING TO 



form, the swollen part being composed of spongy parenchymatous tissue 

 •containing air. Both surfaces of the leaf are densely covered with 

 minute depressed hairs, which protect the leaves from being wetted. 



Envelope of the Corpuscles of Ephedra.* — M. P. Jaccard has 

 •studied the mode in which the envelope of the corpuscles of Ephedra 

 becomes disorganised, and the proteinaceous substances accumulate in 

 the aichegones. The disorganisation probahly takes place unler the 

 influence of a ferment, and the transference of the proteinaceous sub- 

 stances by dialysis through cell-membranes and the wall of the arche- 

 gone, which is connected with the envelopes of the corpuscle by numerous 

 filaments of protoplasm. The membrane is never perforated as is the 

 case with Cycas. The function of the envelope of the corpuscles appears 

 to be analogous to that of the antipodals and of the epithelial layer of 

 the embryo-sac of Composite. I 



Hydathodes of Scolopia.J — M. J. Briquet describes the hychithodes 

 in several species of this genus belonging to the Flacourtiaceae. They 

 consist of two small symmetrical cylindrical-conical appendages at the 

 apex of the leaf -stalk, containing a central tracheid-bundle surrounded 

 by a delicate parenchyme destitute of cellulose and containing calcium 

 oxalate and water. The epiderm possesses water-fissures. These struc- 

 tures are not extranuptial nectaries, since they contain no sugar. 



Thallus of Rafflesia.§ — Dr. F. Schaar gives the following account 

 of the structure of the myceloid thallus of Rafflesia Bochussenii, and its 

 parasitism on roots of Cissus. The thallus is entirely cellular, contain- 

 ing neither tracheids nor sieve-tubes. As a rule the cells of the parasite 

 are sharply differentiated from those of .the host-plant. The hyphsB 

 permeate the leptome-portion of the secondary cortex, the xyleni-discs, 

 and the amylaceous medullary rays; the cells found in the cambium 

 zone of the host have a meristematic character. Jn the leptome the 

 hyphae pass into the cavities of the sieve-tubes, and the membrane of the 

 parasite partially coalesces with that of the host ; the coalescing por- 

 tions are usually very thin. Small haustorial structures are sometimes 

 formed. The bundle-tissue which passes into the flowers of the parasite 

 consists of about 20 bundle-rings placed in a circle, each having its own 

 cambium- ring, which forms sieve-tubes outwardly, the centre consisting 

 of a parenchymatous cellular tissue. 



Roots of Cactiform Euphorbias.]] — M. L. Gaucher calls attention 

 to the structure of the roots of the cactus-like species of Euphorbia, 

 which are well adapted to absorb every particle of moisture out of the 

 dry soil in which they grow. The ultimate ramifications of the root are 

 completely covered by long root-hairs ; and these rootlets themselves 

 become detached and fall off after the absorbing hairs have completed 

 their function. The long roots are characterised by the great develop- 

 ment of the bark and the reduction of the cortical parenchyme and 

 phloem. In the reduced cortex are a great number of wide laticiferous 



* Arch. Sci. Phys. et Nut., viii. (1899 ) p. 190. t Cf. this Journal, 1899, p. 297. 

 t Bull. Lab. Bot. Univ. Geneve, iii. (1&99) pp. 35-6. See Bot. Centralbl., lxxix. 

 (1899) p. 317. § SB. k. Akad. Wiss. Wien, cvii. (1899) pp. 1039-56 (3 pis.). 

 || Jouru. dc Bot. (Morot), xiii. (1899) pp. 173-5 (1 fig.). 



