990 SUMMARY OF CURRENT RESEARCHES RELATING TO 



stem to the immediate flower- stalk is marked by a decreased development of 

 tissue, a rapid diminution in the number of bundles, and reduction of the 

 j)ith. When the fruit is ripe the diiference consists only in a diminished 

 number of bundles and reduction of the pith, together with the absence of 

 secondary vessels. Up to the period of ripening, the mechanical elements 

 within the inflorescence are becoming gradually strengthened, which may 

 take place either in the woody parenchyma or in the hard bast. In other 

 cases, an extra-cambial sclerenchymatous ring or other form of scleren- 

 chyma, makes its appearance, or a secondary sclerosis takes the place in 

 the pith. The conducting tissue is also strengthened, and in some cases 

 the cortical tissue. Not unfrequently the fruit-stalk is thickened imme- 

 diately beneath the fruit. 



Comparative Anatomy of Flower- and Fruit-stalks.* — Herr F. Besser 

 classifies under four heads a large number of flower- and fruit-stalks 

 examined by him, viz. (1) The flower-stalk has no mechanical tissue and 

 the fruit-stalk only bast (Linum usitatissimum, Prunus Cerasus, Platycodon 

 grandifiorus, Monocotyledons) ; (2) The flower-stalk has collenchyma, the 

 fruit-stalk also bast (Cucurhita Pejc/o, Citrullus vulgaris, Papaveraceae) ; 

 (3) The flower-stalk has collenchyma, the fruit-stalk also libriform (^Cam- 

 panula lactiflora, Scahiosa, Asterocephalus hracMatus) ; (4) The flower-stalk 

 has collenchyma, the fruit-stalk also libriform and a much smaller quantitj' 

 of bast (Malvacese, Solanacese). Asparagus officinalis stands alone with its 

 strongly developed sclerenchymatous tissue. 



Bast-cells with vertical transverse walls are common ; libriform fibres 

 also occur. Notwithstanding the temporary duration of these organs, it is 

 not uncommon to find a more or less complicated assimilating system. 



Blossom on Old "Wood.f — Dr. P. Esser remarks that many plants, 

 especially tropical ones, produce flowers on parts of the wood which are 

 several years old. After enumerating examples, he refers to Wallace's 

 suggestion that flowers so produced near the stem, and under the shadow 

 of the leaves, are for fertilization by the shadow-loving butterflies of 

 tropical forests, and also to Johow's belief that by flower-bearing on old 

 and hard parts, a plant is enabled to bear the weight of much larger and 

 heavier fruits that it could otherwise support. He then gives the details 

 of his own experiments on Cercis, Goethea strictiflora, TlieopJirasta, Ficus 

 Poxburghii, and Chrysophyllum Cainito. He treats, in each case, of the 

 anatomy of the wood ; of the formation of a larger number of buds than is 

 common; of the way in which these buds develop© further; and of the 

 manner in which their connection with the vessels of the stem is ultimately 

 recovered. 



The conclusions from these observations he sums up as follows : — 



(1) There is no such thing as the production of adventitious buds upon 

 wood whose development is once completed ; but flowers appearing on old 

 wood come rather, as Johow correctly indicated, from early formed buds 

 which have been resting. 



(2) With regard to the formation of these buds, which are all placed 

 in the axils of leaf-shoots, we must distinguish between the following 

 cases : — 



(a) In each leaf-axil several buds are formed in series, most of which 

 produce inflorescences after shorter or longer periods of rest. (CJiryso- 

 pthyllum.) 



* Besser, F., ' Beitr. z. Entwickelungsgesch. u. Vergleich. Anat. v. Bluten- u. 

 Frucht-stielen,' 32 pp., Lossnitz, 1886. See Bot. Ceiitralbl., xxxi. (1887) p. 93. 

 t Verb. Naturh. Ver. Bonn, xliv. (1887) pp. 69-112 (1 pi.). 



