Oe Ga ae BEING pre ret i ae eames eee tae SORT Reel NRE NE? ea eee 
rgto] CURRENT LITERATURE 391 
“A study of the histology of the stem of the wax plant, Hoya carnosa (L.) 
R, Br.,” by Joun I. Norturop.—J. M. C. 
NOTES FOR STUDENTS 
Prothallia of Lycopodium.—BRUCHMANNS has completed the life histories 
of L. clavatum, L. annotinum, and L. Selago, with an account of the grow 
of the prothallia from the germination of the spores to the maturing of the 
Sex organs, and with the study of the embryo development of L. Selago. Pre- 
viously the germina tion of only three species was known, all with a prothallium 
containing chlorophyll and belonging to the cernuum type: L. salakense, 
independent in development and free from a fungus; L. cernuum; and L. 
inundatum, dependent for complete development upon an endophytic fungus. 
The germination of the spores was secured by sowing them in the forest 
where they were found. This was done in two ways: (1) by putting spores 
and species of fresh strobili into flower pots in potting soil (peat, leaf mold, 
Manure, sand) and forest soil and sinking them in the ground; and (2) by 
mixing spores with forest soil and burying them in holes 10 cm. deep. The 
germination of L. Selago occurred in 3-5 years after sowing; that of L. clavatum 
and L. annotinum in 6-7 years. Prothallia bearing mat organs appeared 
first in L. Selago 6-8 years after sowing; in L. clavatum and L. annotinum in 
12-15 years. Practically all the spores of a sporangium of L. Selago germi- 
nated, but only about 5 per cent of those of other species. All three species 
develop independently a five-celled chlorophyllose prothallium, after which 
a fungus is necessary to complete the development. . clavatum and L. 
annotinum develop in the same way, while L. Se/ago forms a type by itself. 
The first division, an irregular one, cuts off a small lens-shaped cell at the 
base of the spore. Although containing food substances, it is poor in cyto- 
plasm and never enlarges. BRUCHMANN considers it a rudimentary rhizoidal 
Cell, homologous with the first rhizoid of the true ferns. The second division, 
occurring after the spore coat bursts, extends an oblique wall from base to 
apex, bent toward the rhizoidal cell. While in the clavatwm type this wall 
divides the prothallium into hemispheres, in the Selago type it is sharply bent 
away from the rhizoidal cell, making the resultant cells unequal. The differ- 
ence in direction determines the type of prothallium. The basal cell next to. 
the rhizoidal cell never divides. Its sister cell cuts off an inner wedge-shaped’ 
cell and an outer apical cell. A fourth wall divides the wedge into an outer 
Peripheral and an inner or central cell. In L. Selago the wedge-shaped cell 
1S considered the first segment cut off from the apical cell. 
From this point BRUCHMANN divides the growth of the prothallia into 
three periods, depending upon change in direction and manner of growth. 
enn teenies 
_ SBrucumann, H., Die Keimung der Sporen und die Entwicklung der Prothal- 
lien von Lycopodium clavatum, L. annotinum, und L. Selago. Flora 101%:220-267. 
oO. 
: Jigs. 35+ I9gt 
