228 NATURAL SCIENCE. April, 



plant, a Romulea, five inches or more in height, which finds its nearest 

 ally far south in the mountains of Namaqualand. A fine Gladiolus 

 (rightly named splendidus) nearly four feet high, with a fifteen-inch 

 spike of eight splendid crimson flowers, is another good find in these 

 high altitudes. Mr. Taylor has also sent specimens from the low coast 

 ranges, the Rabai and Giryama and Shimba Hills, near Mombasa 

 and from the district between the coast at Zanzibar and Uyui, near 

 Tabora, in Unyamwezi Country. Of special interest is a new screw- 

 pine from the Rabai Hills, the fruits of which resemble those of a 

 well-known Madagascar species, while in its male flowers it is totally 

 different from any of its neighbours, and resembles most nearly a 

 species from New Caledonia. We hope that Mr. Taylor's duties as 

 a missionary will not prevent him from making further botanical 

 explorations with results as valuable as those to which we have just 

 referred. We remember with gratitude what is owed to another 

 missionary, the Rev. R. Baron, in connection with the botanical 

 and geological exploration of Madagascar. 



The Function of Stomata. 



Everyone knows that the leaves of plants are furnished with a 

 number of little mouths with moveable lips, the so-called stomata. 

 In some plants these occur on both surfaces of the leaves, usually 

 being more abundant on the under surfaces, but occasionally being 

 more abundant on the upper surface. In some cases they are 

 altogether absent en one surface. There is dispute as to their exact 

 function. It would seem natural to suppose that they are the chief 

 means by which the gases of the air enter the plant, and it is certain 

 that through them water-vapour leaves the plant. Recently, the 

 most usual opinion among botanists has been that carbonic acid is 

 taken in through the cuticle all over the surface of the leaf, not by the 

 stomata. Mr. F. F. Blackman has communicated to the Royal 

 Society (Proceedings, no. 342, Feb., 1895) the results of some experi- 

 mental investigations he has made upon these points. By means of 

 a new process for estimating small quantities of carbonic acid — a 

 process which he describes briefly — he has succeeded in making more 

 exact observations than hitherto have been possible. He finds that 

 under normal conditions the stomata afford the sole pathway for car- 

 bonic acid into or out of the leaf. Under abnormal conditions, when 

 the stomata or the intercellular spaces with which they communicate 

 are blocked, passage of the gas may occur through the cuticle by 

 osmosis. He also found that Garreau's well-known experiment, in 

 which there occurs exhalation of carbonic acid from a leafy shoot in 

 bright light, is due only to the imperfection of the conditions, to the 

 presence of immature parts or of tissues not fully illuminated. 

 " Mature isolated green leaves fully illuminated assimilate the whole 

 of their respiratory carbonic acid, and allow none to escape from 

 them." 



