ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 97 



minimum. (5) Precipitations wliicli take place with a high minimum 

 always delay the first blossoming. (6) Precipitations with a low 

 minimum always result in early blossoming. (7) Moisture preceding 

 the first blossoming always causes retardation. (8) Deficiency of 

 moisture causes early blossoming when the daily minimum is low, late 

 blossoming when the daily minimum is high. (9) Frosts cause a 

 delay in the first blossoming when they do not kill. (10) Irregu- 

 larities in the normal succession are proportionate to the difference in 

 organization of the species concerned and to the intensity of the factors 

 which compensate the effects of the mean daily minimum. (11) Inver- 

 sions are extreme cases of this irregularity, and are usually the result 

 of precipitations of moisture. (12) Plants with deep roots are less 

 affected by drought than by moisture ; the former acts chiefly on those 

 which do not root deeply. 



Protection of Plants from the Lower Fungi.* — W. 0. Focke 

 points out that plants, especially in their older portions, and dui'ing 

 the resting periods of their active life, are little fitted to withstand 

 the attacks of the lower fungi, and that there are certain means of 

 protection provided them against the attacks of these enemies, which 

 accounts for their suffering so comparatively little from them. 



As such, he names a firm epidermis, especially when it is protected 

 by a coating of wax against the retention of moisture. A fiu^ther pro- 

 tection, especially to stems, is the corky layer of the bark, which, 

 besides being itself a very resisting substance, often contains chemical 

 matters which are injurious to the lower organisms, for example, 

 poisons, tannin, alkaloids, and wax. The underground portions of 

 plants, especially of those growing in marshes, secm"e themselves, partly 

 by a firm epidermis, partly by means of the chemical substances named 

 (tannin for example in Alnus and Comarum, alkaloid in Cicuta, &c.). 

 Evergreen leaves have also, besides their protection against plant- 

 eating animals (spines, poisonous qualities, and leathery consistence), 

 such safeguards as are necessary against the attacks of fungi, and 

 which again consist of a firm epidermis (Ilex), and the possession of 

 some one or more chemicals (poison, alkaloids, &c.). The durability 

 of the succulent fruits which serve such a distinct purpose in the 

 propagation of plants by animals (birds), appears in many cases like- 

 wise to have been caused by these means ; while in regard to seeds 

 which for the most part remain dormant during the winter, either in 

 or upon the earth, these are both protected and preserved by their 

 stout outer covering and by similar chemical substances. Further, 

 the author believes that the fatty oil so frequently found is as valuable 

 for protection as for nourishment. The oil, as well as the husks, 

 checks the absorption of water at a low temperatm-e, without which 

 the dry seeds cannot be attacked by the fungi of putrefaction. The 

 volatile oils also serve in many plants as a protection against injury 

 by the sun. When there is any scarcity of water in the soil, by their 

 evaporation they lower the temperature ; and, according to Tyndall, 

 when these oils are present only in a small degree in the air, they 



* Kosmos, v. (1882). See Bot. Centralbl., xi. (1882) pp. 64-5. 

 Ser. 2.— Vol. III. H 



