ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
57 
phenomena are frequently set up. In the course of its normal growth 
the membrane of the pollen-tube undergoes thickening of a very 
similar nature to that which has been observed in the bast-cells of the 
Apocynaceae and Asclepiadeae. This is effected neither by apposition 
nor by iutussiisception, but by the production of new masses of cellulose 
out of the protoplasm. The thickening is indicated by the silky 
refraction of the tube. It frequently takes the form of a number of 
caps formed successively within the apex of the tube. The separation 
of the protoplasm into distinct masses sometimes gives the appearance 
of a septated pollen-tube. 
Morphology and Physiology of Pulpy Fruits."^ — Mr. J. B. Farmer 
states that the morphology and physiology of the pulp of succulent 
fruits remains almost an untouched field. It is a fact worthy of notice 
that, while pulpy fruits are very common in certain natural orders, so 
much so as to constitute one of the ordinal characters, the morphological 
nature of the pulp itself may vary considerably within a very narrow 
limit of affinity. Amongst British plants the Caprifoliaceae afford 
perhaps the best examples of this ; thus, in Lonicera Periclymenum not 
only the pericarp and placenta become fleshy, but also the bracts and 
axis of the inflorescence ; in the nearly allied L. Caprifolium, however, 
the succulent tissue is derived from the placenta and pericarp alone. 
Besides the extreme case of the honeysuckles and the more common 
forms of berries and drupes, there are some plants, as the rose and the 
strawberry, where the entire pulp is derived from the receptacle; in 
others the floral envelopes contribute the chief portion, as in Hippophae 
and Morus. Another and more irregular source of pulp is the aril, as 
in the yew. Even in berries the relative parts played by the placenta 
and pericarp show great variety in different plants. Thus, in Vitis 
each furnishes about half, in Solarium Dulcamara the placenta, and in 
Ligustrum vulgare the pericarp provides almost the whole pulp. 
The author then deals in detail with three forms of common occur- 
rence which illustrate some of the varieties which are found in the 
nature and formation of pulp. In the ivy we have a plant where the 
pulp is mainly derived from the tissue of the carpels ; and from the 
very first this tissue is clearly marked off from the peripheral cells 
which owe their presence to the activity of the meristem ; since in the 
carpels the cell-divisions occur irregularly, and without definite order, 
except in the few layers destined to form the parchment-like endocarp. 
In the blackberry a portion of the pericarp only is devoted to the 
formation of pulp, the remainder undergoing modification to enable it to 
meet other and special requirements ; while in Solarium Dulcamara we 
meet with a case in which the pulp owes its origin to two sources, being 
derived partly from the wall of the superior ovary, and partly from the 
tissue of the placenta. The author traces the formation of the pulp in 
all these three last cases. 
Branching of Vegetative Axis and Inflorescence.! — Dr. J. Velo- 
novsky describes the mode of branching of the axis of Taxodium disticlium 
(sympodial), Luzuriaga radicans (Smilacineae), and MyrsipJiyllum angus- 
* Ann. of Bot., iii. (1889) pp. 393-413 (2 pis.). Cf. this Journal, 1889, p. 244. 
t SB. K. Bohm. Gesell. Wiss., 1888, pp. 365-76 (1 pi.). 
