214 THE JOURNAL OF BOTANY 



enumerating the earlier formations in which plant-remains con- 

 jectured to belong to ancestors of the group had been found, he 

 stated that the earliest known remains of undoubted CharacecB 

 were detached fruits recorded from the Lias and Oolite, the earliest 

 remains of the vegetative parts being those in the Middle Purbeck 

 beds. He explained that by Mr. Reid's method of subjecting 

 slices of the limestone, in which the plants were found, to a pro- 

 longed drip of very slightly acidulated water, so that the Chara- 

 remains were etched out, they had been able to elicit much fresh 

 information as to structure, which had not been obtainable from 

 the sections and polished surfaces of chert. Some lantern-slides 

 and a large number of photographs taken by Mr. Reid were ex- 

 hibited with especial reference to the prevalent type of Characeous 

 plant which had recently been described by Mr. Reid and himself 

 as a new genus, Clavator. The principal characteristics of this were : 

 the constant number of the cortical tubes (12), the remarkably 

 swollen stem-nodes developed in a peculiar manner, the production 

 of symmetrical rosette-like groups of small clavate processes on 

 the stems and branchlets, and the presence of an utricle enveloping 

 the oospore and formed or surrounded by a number of elongated 

 adnate cells, all of which characters represented important diver- 

 gencies from any existing type of Characeous plant. Reference 

 was made to other types which had not yet been worked out, 

 especially to a large one of which casts only had been found and a 

 minute one evidently belonging to the section Nitellece, but pre- 

 senting important points of difference from existing forms. 



At the same meeting Prof. Julius MacLeod, University of 

 Ghent, gave an account of his paper on " Quantitative Variation 

 in certain Diagnostic Characters of ten Species of the Genus 

 Mniuniy He asked whether it was possible to describe and to 

 identify an animal or a vegetable species by means of numbers 

 representing the value of the specific characters ? He had tried to 

 realise this by measuring thirty-eight characters in about ninety 

 species and twenty varieties of the genus Carabus, and to carry 

 out similar work with mosses of the genus M7im7n, limiting himself 

 to the study of the leaves of the fertile stem of ten species of that 

 genus. When we measure, for instance, the length of the succes- 

 sive leaves from the base to the summit of a fertile stem of a Mniwn, 

 we see that the length increases up to a maximum and then 

 diminishes. This curve represents the variation of the character 

 under consideration along the axis. This peculiar form of varia- 

 tion may be called gradation. It is something quite different from 

 variation properly so called. The gradation of the measured 

 characters of the ten species shows much diversity. In these 

 examples it is possible to find the name by four characters ; of 

 course we may often be compelled to make use of five or more 

 characters. As we have at our disposal a dozen characters, we 

 may hope that the identification of a given specimen will be always 

 possible, even if the species were more numerous. 



On the same occasion Dr. Daydon Jackson communicated a 

 note from Miss Louisa Pershore, of Torquay, stating that Mimulus 

 moschakcs had been observed by her for several years as growing 



