516 BOTANICAL GAZETTE [DECEMBER 
had in a year or two from seed. It is suggested, however, that cuttings will 
generally prove more desirable. Of much importance is the fact that in 
CovILLE’s experiments there were produced berries much beyond the usual 
ize. The experiments were made chiefly on Vaccinium corymbosum, but it is 
believed that other species would show similar behavior. 
In one of the later papers, CoviLte describes the changes in the formation 
of leaf mold, noting its early acidity and its subsequent alkalinity; whereas, 
peat (not only lowland peat, but also upland peat, as he terms it) retains its 
acidity, because of the comparative suspension of decay. In another paper, 
he urges farmers to utilize some of their acid soils by the growth of acid-tolerant 
plants, and not universally to neutralize them by the use of lime. The wor 
_ of CovILte is an excellent roa of the application of ecological methods 
to agriculture.—H. C. Cow 
Sexuality of Mucorales.—In his studies on the sexuality of the Mucorales, 
BLAKESLEE observed that the sporangium originating from the zygospore of 
Phycomyces nitens contains spores which with respect to sexual differentiation 
are of three types, giving rise respectively to plus, minus, and neutral mycelia. 
To account for the occurrence of these three sexually differentiated strains, 
BurGEFF%’ has formulated a hypothesis according to which the nature of the 
mycelium is determined by the nuclei which it contains. These may be either 
(+) or (—), and, since the spores contain one or more nuclei, it is evident that 
a particular spore may contain either all (+-), or all (—), or both (+) and 
(—) nuclei. In the first two cases, the spores and the mycelium which they 
produce are said to be “homokaryotic,” and in the other case “heterokaryotic.” 
This hypothesis he tested in an ingenious manner. By inserting the tip of a 
young sporangiophore into the cut basal end of another of the opposite strain, 
and applying pressure to the wall of the outer one, he was able to rupture the 
tip of the inner hypha and bring about a mixture of the two masses of proto- 
plasm with their eapective (+) and (—) nuclei. Cultures from the sporangia 
produced by this “mixochimaera” gave (+), (—), and neutral mycelia. 
He describes an analogous case of heterokaryosis presented by Phycomyces 
nitens var. piloboloides, which differs from the parent in the form of its sporangio- 
phores. The spores of this variety give rise to mycelia which produce either 
nilens sporangiophores only, or piloboloides sporangiophores only, or both 
Ss mixed on the same mycelium. The homokaryotic types remain pure, 
but the mixed type continues to split in the manner described. Mixochimaeras, 
formed from the pure selected types, give rise to all three forms. Crosses © 
P. nitens with rigidly selected strains of the variety give rise to all possible 
forms of both (+) and (—) strains of both types and to heterokaryotic com- 
binations. The production by means of the cross of a (—) strain of var. 
piloboloides, which is (+), is of special interest —H. HASSELBRING. 

7 Burcerr, H., Uber Sexualitat, Variabilitat, und Vererbung bei Phycomyces 
nitens. Ber. Deutsch. Bot. Gesells. 30:679-685. 1913 
