BUDS. 



[ 102 ] 



BURSARIA. 



22. Br. pyriforme, Sw. 



23. Br. Ludwigii, Spr. 



24. Br. crudum, Schreb. 



25. Br. nutans, Schreb. 



26. Br. elongatum, Dicks. 



BUDS. The buds of plants form interest- 

 ing objects of microscopic investigation on 

 many accounts. First in tracing the deve- 

 lopment of the organs, and also of the tissues 

 of which these are formed; secondly, on 

 account of certain temporary structures which 

 they exhibit. The thick epidermis of the 

 scales of the winter-buds of ordinary trees, 

 as of the ash, &c., is a very favourable object 

 for sections to show the character of this 

 tissue when highly developed. The internal 

 soft scales and young leaves of very many of 

 these winter-buds, as well as other buds of 

 herbaceous plants, are clothed with glandular 

 hairs, which disappear when the buds have 

 expanded, and these often afford advantageous 

 material for studying cell-development. 

 These glandular hairs were mistaken by 

 Griesebach (Botanische Zeitung, ii. p. 661, 

 Sanderson, Ann. N. Hist. 2 ser. xvi. p. 141) 

 for bodies analogous to the antheridia of 

 Mosses. See GEMMAE. 



BUG. See CIMEX. 



BULBOCELETE, Ag. A genus of Che- 

 tophorese (Confervoid Algae), forming dense 

 villous tufts 1-4" or 1-2" high, on freshwater 

 plants, &c., in lakes and pools, remarkable 

 for the structure surmounting its reproductive 

 cells, namely a slender elongated cell repre- 

 senting a bristle with a bulbous base. Hassall 

 supposed that a kind of conjugation took 

 place in this genus like that he assumed to 

 occur in (Edogonium (Vesiculifera], but this 

 does not appear to be correct. The fertile 

 cells are borne at the side of the upper end of 

 cells of the filaments; they are large, globular 

 or oval, and surmounted by the bristle-cell 

 (fig. 87), which often exists upon the 



same point of the 

 stem-cell, without 

 any intermediate 

 sporiferous - cell. 

 The history of the 

 reproduction, as 

 given by Alex. 

 Braun,is as follows. 

 A branch is deve- 

 loped from the 

 upper end of a 

 stem-cell by a 

 pouch-like protru- 

 sion of the wall ; 

 when this has at- 



Fig. 87. 



Bulbochsete setigera. 

 Portion of a filament with a 



sporiferous .cell. 

 Magnified 150 diameters. 



tained a certain size, the green contents of the 

 parent-cell pass into it, leaving about half (the 

 lower) of the parent-cell empty of coloured con- 

 tents, and a septum then cuts the parent-cell 

 in the middle, so that two cells are formed, the 

 lower uncoloured, the upper green; the pro- 

 truding branch increases in size and expands 

 into a globular form, and then the rest of 

 the contents of the parent-cell (from the 

 upper half-cell) pass into it, and it also 

 becomes shut off by a septum. The bristle- 

 cell (with sometimes a small intermediate 

 cell) is formed after the sporiferous-cell has 

 been shut off by the septum from the stem- 

 cell. 



The contents of the sporiferous-cell subse- 

 quently exhibit two kinds of development. 

 They either become isolated in their parent- 

 cell, acquire a thick proper membrane and 

 thus form resting -spores, which assume an 

 orange colour in autumn, or they accumulate 

 in like manner in the centre of the cell, 

 produce no membrane there, however, but a 

 crown of cilia. In either case they escape 

 from the parent-cell by the disarticulation of 

 the bristle-bearing cell, and the rupture of 

 the membrane of the sporiferous cell at that 

 point. Then the resting-spore falls out me- 

 chanically, while the ciliated body escapes by 

 active motion of its cilia as a zoospore or 

 active gonidium, which after a time comes to 

 rest, produces a membrane over its whole 

 surface and germinates as a spore. 



B. setigera, Ag., is a common plant, and 

 is variable in the relative length and diameter 

 of its cells, on which ground Kiitzing has 

 separated a JB. minor, when the diameter is 

 equal or greater than the length. Hassall, 

 Fr. Conf. pi. 54. figs. 1-4; Dillwyn, Conferv. 

 pi. 59. 



BIBL. Alex. Braun, Verjungung in der 

 Natur. (Rejuvenescence, fyc., Ray Volume, 

 1 853), passim ; Hassall, Ann. Nat. Hist. xi. 

 36; Br. Freshw, Conf. 209. pi. 54; Decaisne, 

 Ann. des Sc. nat. 2 ser. xvii. 335. pi. 14. 

 fig 5 ; Kiitzing, Species Alg. 422. 



BUNT. A disease of Cereal Grasses, Sec., 

 depending on Fungi. See BLIGHT. 



BURSARIA, Ehr. A genus of Infusoria, 

 of the family Trachelina. 



Char. Body ciliated all over ; anterior 

 portion projecting beyond the simple eden- 

 tulous mouth : no tremulous lamina. 



Locomotion is effected by cilia usually 

 arranged in longitudinal rows, and somewhat 

 larger ones generally surround the mouth. 



Ehrenberg describes fourteen species. 

 They are mostly found in stagnant fresh 



