106 



flavescens, its American analogue, at least here in southern Cali- 

 fornia, Mistletoe is very abundant, and at the proper season one 

 may find seeds glued on branches of trees, on fences and stones, 

 in short, wherever birds alight. I have never seen any that had 

 the appearance of having passed through the digestive tract of 

 a bird. They seemed rather as if left by the bird in cleaning his 

 bill or feet, to which they may have adhered while he was feed- 

 ing. This is more probable from the fact that seldom do more 

 than two or three seeds appear to have been deposited at one 

 time. Young mistletoes usually, but not always, start from the 

 upper half of the branch on which they grow. 



Why P. flavescens should be leafy and P. jiinipcriimni leafless, 

 has been plausibly explained from the fact that the first species, 

 growing on deciduous trees, needs leaves of its own during the 

 resting period of its host, while the juniper mistletoe needs none 

 since it grows on evergreens. This is a satisfactory explanation, 

 but it evidently needs amendment to make it clear why P. Bol- 

 leanum, growing on junipers, should be leafy, while P. Cali- 

 fornicum, which is parasitic on the mesquite and other deciduous 

 hosts, is leafless. 



San Bernardino, California. 



REVIEWS 



The Comparative Embryology of the Rubiaceae * 



The second part of Professor Lloyd's study has recently 

 appeared and forms a very valuable as well as interesting contri- 

 bution to our knowledge of the Rubiaceae. In this paper there 

 are studies of the following species : Callipcltis Cucullaria, Sher- 

 ardia arvensis ; several species of Galium, viz., Aparine, recurvum, 

 pilosum, Mollugo, verum, triflorum, tinctorum and Parisiense ; 

 several species of Aspcrida — azurea, galioides, montana, sctosa, 

 and tinctoria ; Rubia tinctoria ; Crucianella gilanica, C. macro- 

 stachya, C. herbacea ; Diodia Virginiana, and D. teres ; Richard- 

 sonia pdosa ; and Houstouia cocrulea and H. longifolia. 



* Memoirs of the Torrey Botanical Club, 8 : 27-112. pi. 5-/5. 15 F. 1902. 



