{gor | CURRENT LITERATURE 433 
cell of the rhizoid they seem to play the same réle as (according to Némec) 
the starch grains do in the cells of the root tip.—C. R. B. 
STRASBURGER ® has recently investigated the formation of pollen in 
Asclepias Cornutt and Cynanchum vincetoxicum, having in view chiefly the 
reported lack of tetrad formation in some of the Asclepiadaceae. A primary 
sporogenous cell develops directly into a spore mother cell, as in Malva, 
Datura, Mentha, and Chrysanthemum, being recognized by the reduction in 
the number of chromosomes. Each mother cell gives rise to four pollen 
grains as in other plants, but instead of lying in the usual tetrad form they 
. develop ina row. This leaves the Cyperaceae as the only group known to 
form only one pollen grain from each mother cell. The row of four micro- 
Spores is homologized with the row of four potential megaspores commonly 
produced by the primary sporogenous cell in the nucellus. The regularity 
in the arrangement of the cells and the he A of the protoplasm 
invited a search for centrosomes, but none were foun he author, while 
not denying the existence of centrosomes in the ey plants, expresses an 
increasing doubt as to the possibility of making such structures visible with 
the present methods.—T. C. FRYE. 
FREDERICK H, BILLINGS ® has examined a number of species of several 
large families of spermatophytes to see whether the seed development, espe- 
Cially the changes of the embryo sac and integuments after fertilization, can 
be used as a basis of classification. Taking plant groups as now recognized, 
in some he finds marked resemblances. For example, in all species of Cam- 
panulaceae, Lobeliaceae, and Stylidaceae he finds “ haustoria’’ (outgrowths 
from the embryo sac) at both chalazal and micropylar ends, and these are 
Supplied with nuclei from the endosperm. The antipodal ones break down, 
but may divide first ; while in Calendula the micropylar haustorium is said 
to be under the control of the persistent synergid, which grows into it. The 
various kinds of haustoria are described in detail. In some cases the embryo 
Sac is constricted, the upper chamber containing the embryo, the lower 
becoming filled with tissue. In other cases finger-like processes put out 
om the side or base of the sac, reaching towards the region of vascular 
bundles. The author’s reason for assigning a nutritive function to the 
“haustorium ”’ regions is simply the active appearance and staining power of 
the nuclei. His conclusions are that in doubtful cases the nature of the 
embryo sac, the thickness of the integument, etc., may help to settle the sys- 
tematic position of a genus or species.— FLORENCE May Lyon, 
* Einige Bemerkungen zu der Pollenbildung bei Asclepias. Ber. deutsch. bot. 
Gesell. 19: 450-461. pl. 2g. 1901. 
*® Beitrage zur Kenntniss der Samenentwickelung. Flora 88 : 253-318. 1901. 
