1904 | CURRENT LITERATURE 71 
tuberization studies.“ EE, Laurent had shown that buds from aerial stems of 
the potato may develop into tubers, when placed in a sufficiently concen- 
trated solution of saccharose, even when the latter is thoroughly sterilized ; 
which seemed to cal] in question Bernard’s theory that tuberization is due to 
an infection by parasitic fungi. Bernard confirms Laurent’s results and 
extends them considerably, showing that a number of solutions produce like 
results. In these cases the chemical nature of the solution is shown to be of 
but little moment as compared with osmotic pressure. Bernard therefore 
enlarges his theory as follows: the state of hypertrophy which we cail 
tuberization may be induced by various agents, which bring the cells into 
contact with substances of relatively high osmotic pressure. Among these 
substances in nature the products of fungus activity are perhaps the most 
important.—H. C, COWLEs. 
IN HIS second paper on the solenostelic ferns Gwynne-Vaughan * extends 
his observations to a large number of genera which he treats in a comparative 
way. His studies have led him to abandon Van Tieghem’s term polystelic, 
for he finds that the meristeles are in all cases segments of a vascular ring, 
the lacunae in which are caused by the exit of leaf traces. The term solen- 
ostelic is applied to those cases where the foliar lacunae do not overlap, and 
this condition is derived from one in which the stele is solid. Evidence is 
adduced to show that the intrastelar parenchyma is merely cortex which has 
intruded through the leaf-gaps. Thus Gwynne-Vaughan’s view of the fern 
stele coincides with that already advanced by Jeffrey, although rather 
strangely no mention is made of this fact, and is opposed to that of many 
English writers. The internal vascular strands found in Cyatheaceae are con- 
sidered to be derived from elaboration of a local thickening of the xylem ring 
at the margin of the leaf gaps. The present system of classification is 
considered to receive support from the anatomical data presented, since 
nearly all the genera regarded as primitive by Prantl have a primitive 
vascular structure.—M. A. CHRYSLER. 
THE SPERMATOGENESIS of hybrid peas * appears as the second paper in 
Dr. Cannon’s studies in plant hybrids. Two hybrid peas were used for the 
present investigation, one a hybrid between the pure races Fillbasket and 
Debarbieux, and the other between Express and Serpette. Both hybrids are 
fertile and show variation according to the law of Mendel. Spermatogenesis 
was studied both in the pure races and in the hybrids. In the cells of the 
gametophyte the number of chromosomes is seven in all the pure forms and 
™ See Bor. GAZ. 33: 75- 1902. 
5 GWYNNE-VAUGHAN, D. T., Observations on the anatomy of solenostelic ferns. 
II. Ann. Botany 17: 690-742. 1903. 
*6 CANNON, W. A., Studies in plant hybrids: the spermatogenesis of hybrid peas. 
Bull. Torr. Bot. Club 30: 519-543. fds. 17-79. 1903. For review of the first paper 
see Bot. Gaz. 35: 445. 1903. 
