June, 1923] MURNEEK — CHANGES IN BARTLETT PEARS 311 
be used as fairly good indices of the gross seasonal changes of the fruit 
during the time both of development and of maturity. It is to be ques¬ 
tioned, however, whether it would be at all possible to show by means of 
chemical analyses such small differences in maturity as take place in but a 
few, say three or four, days. 
In contrast to our knowledge of the chemistry of the pear, we know far 
less of the important morphological and physical changes that are coincident 
with the development of this fruit. The fundamental work of Kraus, 
McAlpine, Malfatti, Zschokke, and others is, however, of particular sig¬ 
nificance in this respect. They have given us a good conception of the 
gross structure of the pear fruit. Hence their work warrants a detailed 
review. 
Though not considering the pear directly, the analytical researches of 
Kraus (7) on the morphology of pomaceous fruits convey thorough and 
definite information on the character and development of the various 
tissues—vascular, parenchymatous, dermal—forming a pome fruit. Briefly, 
it is to be regarded as consisting of several drupe-like fruits, borne within, 
and connected with, a fleshy torus. The three regions—carpellary, pith, 
and cortical—are clearly distinguishable both as to their ontogenetic 
development and their morphology. Outside of the seed, development of 
the structures consists mainly in the expansion of cells already formed, 
alterations in their chemical content, and the storing of food. It is hinted, 
however, that further cell division may possibly take place in some such 
manner as suggested by Farmer (3). The vascular system permeates all 
parts of the fruit except the pith region, the cortex being particularly well 
supplied. The ten primary toral bundles divide and anastomose, forming 
a complete fibral network under the epidermis. 
The fibro-vascular system of the pear (pome) as it appears in two 
varieties, Harrington’s Victoria and Achan, has been pictured by McAlpine 
(13). Excepting the pith region, it forms a complete and elaborate network 
throughout the fleshy part of the fruit. 
Malfatti (12) describes more in detail the anatomy of the pear, par¬ 
ticularly that of the epidermal region. As a result of growth, epidermal 
cells divide into “daughter” cells. Thinness of the walls indicates which 
are the newest cells. A thick cuticle covers the epidermis. It becomes 
cracked and torn at points where lenticels are formed. The latter are 
underlain with cork. So, too, in case of russeting, epidermal cells anywhere 
may be replaced by cork cells. Below the epidermis is found a subepidermis 
consisting of 3-4 layers of tangentially stretched plate-like parenchymatous 
cells. Ordinary isodiametric cells of the cortex adjoin the subepidermis. 
In addition to protoplasm, they contain small granules of starch, distributed 
either singly or in groups, and sugar in solution, while subepidermal cells 
contain beside sugar also chlorophyll, tannin, and chromoplasts. Stone 
cells, either singly or more frequently in groups, are found imbedded in 
