338 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and some have very narrow xylem vessels, the water-supply being slight 

 and the leaves very small. The mesophyll is well developed and possesses 

 large air-spaces. The plants of the third group are very well fitted for a 

 semi-arid environment, being densely ramified and curling up into a 

 close cluster ; the leaves are placed horizontally on both sides of the 

 stem. The anatomical construction of all species shows a rather thin- 

 walled hypodermis and cortex on the upper (inner) surface of the stem, 

 and thick-walled on the lower (outer) surface. During drought the thin- 

 walled tissue loses water more quickly than the thick-walled ; hence the 

 plant curls inward. Eeopening is due to quicker absorption of water by 

 the thin- walled tissues ; and the plants may increase in weight by 

 42-54 p.c. A considerable amount of oil is found in the cells, in the 

 form of small drops in the protoplasm ; these oil-drops unite and grow 

 larger during desiccation, and possibly form a protecting film around the 

 protoplasm. Hygrophytic species produce no oil, but starch : and it 

 may be that the oil is a reserve food in the xerophytic species, which 

 produce less starch. ' A. G. 



Bulbils of Lycopodium lucidulum. — R. Wilson Smith {Bot. 

 Gazette, 1920, 69, 426-37, figs.). A description of the bulbils found 

 on certain non-strobiliferous species of Lycopodium. The author con- 

 cludes that (1) the bulbil is not the homologue of a branch, since it 

 has only a simple vascular strand and not a complex exarch radial 

 system : nor is it a reduced dichotomy, nor equivalent to the bulblets 

 of Lilium or Allium. (2) It is not the homologue of a sporangium, 

 because inter alia it differs in receiving a prominent vascular strand. 

 (8) It is a transformed leaf, retaining the position, dorsiventrality, and 

 in a great measure the vascular strand of a leaf ; it may perliaps be 

 homologized with an early undeveloped bulblet of a fern. Further, the 

 author describes the origin and vascular bundles of the branches, leaves 

 and bulbils. He ascribes the accumulation of starch in the bulbil proper 

 to the absence of phloem in the narrow neck joining it to the base, and the 

 detachment of the ripe bulbil to the disorganization of the xylem walls 

 in this region. The rate of growth he estimated from the persistent 

 bases of the bulbils ; and he gives some observations on the habits of 

 the plant. A. G. 



Bryophyta. 



Cytology of Bryophyta. I. Spore-formation in Chiloscyphus poly- 

 anthus. — Rudolf Florin {Arkiv for Botanik, 1919, 15, No. 16, 

 1 pL). An account of spore-formation in Chiloscyphus polya?ithus, 

 describing and figuring the presynaptic stage, the strepsinema, diakinesis, 

 metaphase, anaphase, etc. A. G. 



North American Species of Asterella. — Alexander AY. Evans 

 (Contrib. U.S. Nat. Herb. Washington, 1920, 20, 247-812). A 

 monograph of the North American members of this difficult genus, the 

 name of which has been involved in much change and confusion, 

 Asterella Pal. de Beauv. was created in 1805-6 for two of Linn^eus's 

 species, Marchantia tenella and M. hemisphserica. These have long been 



