SCIENCE-GOSSIP. 



217 



THE LEAF-NATURE OF BUD-SCALES. 

 Bv Rudoli Beer. 



M 



Fig. 1. — Typical foliage-leaf — e, 

 epipodium or leaf-blade ; m, me- 

 sopodium or leaf-stalk ; h, hypo- 

 podium or leaf-base ; s, stipule. 



ORPHOLOi; Y 



takes a promi- 

 nent place in interest 

 among the various 

 branches of biologi- 

 cal science ; in its 

 pursuit we have, al- 

 most at every turn, 

 the strangest and 

 most startling facts 

 brought home to us. 

 Parts which to all 

 appearances are 

 entirely dissimilar 

 are shown by this 

 science to be often of 

 the nearest kinship 

 and probably modifications of some common type ; 

 on the other hand, members which present the 

 closest resemblance to one another are frequently 

 demonstrated by morphological methods to be 

 quite distinct in their origin. In no instance is this 

 found to be truer than when the homology of leaf- 

 structures is traced. Here it can be shown that 

 the ordinary foliage leaf, the parts of the flower 

 and the various scale structures which appear on 

 the stem, are all modifications of a primitive ideal 

 form which sums up in itself the different 

 characters which we find specialised in each 

 particular case above mentioned. It is in relation 

 to scale-structures and those more especially which 

 cover and protect the bud, that I would at present 

 speak. 



Everyone is more or less acquainted with the 

 general outward appearance of a bud as it is found 

 on our ordinary forest trees and shrubs. It is a 

 conical body clothed with brown (or greenish) 



membranous scales on the exterior, and packed 

 within with the tender shootlet, which will elongate 

 and burst into the sunlight in the following spring. 

 Evidently the bud-scales are adaptions to protect 

 the young shoot from the frost and cold of winter, 

 and the question which at once suggests itself in 

 this connection is whether these scales are inde- 

 pendent structures or are modifications of some 

 other member already borne on the stem. Botanists 

 have long ago shown us that the latter supposition 

 is the correct one, and they point to the leaf as the 

 member which has been thus adapted. Foremost 

 on the list of those who have investigated this 

 question stands the name of Professor Goebel, and 

 all interested in the subject should refer to his 

 monograph, " Beitrage sur Morphologie et 

 Physiologie des Blattes," which appeared in the 

 " Botanische Zeitung " for 1880. 



Fig. 3.— Development of lamina on bud-scale of horse-chestnut. 



12 3+ 5 



Fig. 2. — Passage of bud-scale of lilac to normal foliage-ltaf. 



Before we proceed to enquire what portions of 

 the leaf are modified to form the protective scales, 

 it is necessary that we should have a clear know- 

 ledge of what these foliar parts are. For this 

 purpose let me refer to the work of Professor 

 Eichler, who many years ago studied the develop- 

 ments of the leaf. 



He tells us that the first indication of leaf 

 formation is a small cellular protrusion appearing 

 just below the growing point. This indifferentiated 

 process he terms the" primordial leaf" ; as develop- 

 ment proceeds, segmentation into various regions 

 takes place. The first division that is apparent is 

 into two parts, a lower and an upper : of these the 

 former normally remains stationary, undergoing 

 but little further alteration, and is known as the 

 " leaf-base " or, to use the scientific term now in 



