392 BOTANICAL GAZETTE [NOVEMBER 
L. Selago resembles closely L. Phlegmaria in development, while L. clavatum 
and L. annotinum are alike. The entrance of the fungus at the peripheral 
or basal cell stimulates the apical cell to division. It cuts off from its two sides 
alternately five or seven segments in the L. clavatum type, and fewer in L. 
elago. ‘This closes the first period. 
Extensive growth of both the prothallium and the fungus characterizes 
the second stage. Rapid radial growth at the apex results in a pear-shaped 
prothallium. The fungus in the two lycopod types of prothallium represents 
two species. In L. clavatum it forms a peripheral digestive mantle surrounding 
the central mass of storage cells. Limited from the central cells by a palisade 
layer, it becomes entirely intercellular. The fungus of Z. Se/ago resembles 
in habit that of L. Phlegmaria and fills the entire prothallium posterior to 
the apical region except the epidermis. The sister cell of a rhizoid, infected 
by a branch of the mycelium from the hypodermis, serves as an ‘“‘ Expeditions- 
zelle.”’ From it the hypha passes out to the substratum, spraying out into 
fine branches. To this cell BRUCHMANN attributes the function of chemically 
attracting the fungus by its enzymes. 
The third period has to do with the changes in the apical region. Marginal 
meristematic cells in L. clavatum surround the axial conductive cells, coexten- 
sive with the former storage cells. Reproductive organs develop on the margin, 
antheridia preceding archegonia. Such prothallia may live twenty years. 
During this period the fungus forms spores. In L. Selago the attempt to gain 
dorsiventrality causes extensive elongation of the prothallium, which at the 
soil surface develops chlorophyll. The apical growth becomes marginal, the 
central tissue acting as a storage region. The outer layers on one side develop 
paraphyses and sex organs; on the other, vegetative cells containing the 
fungus, which always remains intracellular. 
e embryo-development of L. Selago agrees in detail with that of L. 
Phlegmaria. The root appears last, later than in L. clavatum and L. annotinum. 
The foot is smaller than that of L. clavatum and of L. annotinum, but less 
papillate than that of L. Phlegmaria. Its continued growth upward bursts 
the prothallium, whereupon it reaches the light and becomes green.—GRACE 
L. CLApp. 
Variation in timothy.—An important contribution to the subject of 
secular variation has been made by CLarK,° who has studied the variation 
in height, weight of forage produced, earliness of bloom, and duration of the 
period of bloom in timothy (Phleum pratense). Data were secured during 
three successive years on 3505 plants representing 163 pedigrees derived from 
22 different states of the United States. As there can be no doubt that timothy, 
like many other plants which have been studied, consists of a number of distinct 
hereditary forms or biotypes, the extent of variation, which was found to be 
6 Crark, C. F., Variation and correlation in timothy. Bull. 279, Cornell Uni- 
versity. pp. 301-349. figs. 1r1-150. July 1910. 
