Z AN ENUMERATION OF THE BRUNIACE^ 



to the stem. As accessories, parenchymatous cells serving for 

 water storage are present at the apices of the leaves near the 

 termination of the veins, while hairs of a straggly or more com- 

 pact nature render effective service in retarding transpiration, and 

 incidentally lessen the deleterious effects of intense isolation or 

 extremes of temperature. 



Anatomically the order has been investigated by Thouvenin,''' 

 Solereder,t Knoblauch, J Colozza, and Kirchner.§ The last-named 

 author lays special stress upon the occurrence of a corky leaf-tip, 

 and maintains it to be one of the most characteristic points in 

 connection with the Order. |1 According to Kirchner, these tips 

 are formed by a cap of tissue of brown (or black) corky cells, on 

 the inner side of which lies a meristem, from which new cork- 

 cells are produced as the outermost ones become exfoliated ; in 

 Audotiinia this meristematic tissue becomes inactive early in 

 life. Kirchner is of opinion that these corky leaf-tips materially 

 assist in diminishing the harmful effects of intense sunlight, and 

 incidentally also curtail the surface for transpiration. Differ- 

 ences in the distribution of the stomata, which individually are 

 surrounded by from five to seven companion-cells, are correlative 

 with various species, thus : — 



In PseudohcBchea virgata, P. sacculata, P. palustris, Baspalia 

 angulata, B. Dregeana, B. microphylla, B. imsserinoides, and 

 B. squalida, as well as in the majority of Nebelias and Brunia 

 nodiflora,^ they are confined to the appressed upper leaf-surface 

 or occasionally on the lower, in the region where the tips of the 

 preceding leaves overlap. Conversely, the stomata are restricted 

 to the lower side of the leaves in Linconia cuspidata, Thamnea 

 gracilis, and Pseudobceckea cordata ; but in Thamnea depressa 

 Oliv. and Pseudobceckea racemosa they are distributed on both 

 sides, with a preponderance, however, on the lower surface in the 

 case of the latter species. Generally they are irregularly scattered, 

 but in the leaves of Staavia radiata, S. capitella, and Pseudobceckea 

 pialustris they exhibit a marked transverse arrangement. 



The leaves are traversed by from three to twenty veins, 

 according to Colozza ; the hairs which invest those of certain 

 species are always unicellular. The minute, many-celled processes 

 which are disposed laterally at the insertion of the pinoid leaves 

 of Staavia are of considerable biological interest ; they were first 

 detected by Baillon,** and are easily discerned on living plants as 

 black prominences. Kirchner ff has seen them also on Berzelia, 

 and less conspicuously on Linconia cuspidata ; and their inter- 



* Ann. Sci. Nat. xii. 1890, pp. 148-152, pi. 22. 



t Holzstruktur, 118-119, 1885. Syst. Anat. Die. 377-379, and pp. 657-658, 

 1898; Supp. 133-134, 1908: Engl. Trans., by Boodle & Fritsch, i. 333-335, 

 and pp. 581-582, 1908 ; ii. 914-915, 1908. 



X Okolog. Anat., &c., Habilitat. — Schr. Tubingen, 1896, pp. 15 et seq. 



§ Beitrage Kentniss der Brunia. Breslau, 1904, pp. 1-29. 



II Op. cit. 



i\ Kirchner, op. cit. 



** Baillon, Hist. PI. iii. 385. ff Op. cit. p. 28. 



